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Sample records for hindlimb muscle dynamics

  1. Dynamic Foot Stimulation Attenuates Soleus Muscle Atrophy Induced by Hindlimb Unloading in Rats

    NASA Technical Reports Server (NTRS)

    Kyparos, Antonios; Feeback, Daniel L.; Layne, Charles S.; Martinez, Daniel A.; Clarke, Mark S. F.

    2004-01-01

    Unloading-induced myofiber atrophy is a phenomenon that occurs in the aging population, bed-ridden patients and astronauts. The objective of this study was to determine whether or not dynamic foot stimulation (DFS) applied to the plantar surface of the rat foot can serve as a countermeasure to the soleus muscle atrophy normally observed in hindlimb unloaded (HU) rats. Thirty mature adult (6-month-old) male Wistar rats were randomly assigned into ambulatory control (AMB), hindlimb unloaded alone (HU), or hindlimb unloaded with the application of DFS (HU+DFS) groups. A dynamic pattern of pressure was applied to the right foot of each HU animal using a specially fabricated boot containing an inflatable air bladder connected to a solenoid air pump controlled by a laptop computer. The anti-atrophic effects of DFS were quantified morphometrically in frozen cross-sections of soleus muscle stained using the metachromatic-ATPase fiber typing technique. Application of DFS during HU significantly counteracted the atrophic response observed in the soleus by preventing approximately 85% of the reduction in Type I myofiber cross-sectional area (CSA) observed during HU. However, DFS did not protect type II fibers of the soleus from HU-induced atrophy or any fiber type in the soleus muscle of the contralateral control leg of the DFS-treated HU animals. These results illustrate that the application of DFS to the rat foot is an effective countermeasure to soleus muscle atrophy induced by HU.

  2. Hindlimb suspension reduces muscle regeneration

    NASA Technical Reports Server (NTRS)

    Mozdziak, P. E.; Truong, Q.; Macius, A.; Schultz, E.

    1998-01-01

    Exposure of juvenile skeletal muscle to a weightless environment reduces growth and satellite cell mitotic activity. However, the effect of a weightless environment on the satellite cell population during muscle repair remains unknown. Muscle injury was induced in rat soleus muscles using the myotoxic snake venom, notexin. Rats were placed into hindlimb-suspended or weightbearing groups for 10 days following injury. Cellular proliferation during regeneration was evaluated using 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry and image analysis. Hindlimb suspension reduced (P < 0.05) regenerated muscle mass, regenerated myofiber diameter, uninjured muscle mass, and uninjured myofiber diameter compared to weightbearing rats. Hindlimb suspension reduced (P < 0.05) BrdU labeling in uninjured soleus muscles compared to weight-bearing muscles. However, hindlimb suspension did not abolish muscle regeneration because myofibers formed in the injured soleus muscles of hindlimb-suspended rats, and BrdU labeling was equivalent (P > 0.10) on myofiber segments isolated from the soleus muscles of hindlimb-suspended and weightbearing rats following injury. Thus, hindlimb suspension (weightlessness) does not suppress satellite cell mitotic activity in regenerating muscles before myofiber formation, but reduces growth of the newly formed myofibers.

  3. A model for nonexercising hindlimb muscles in exercising animals.

    PubMed

    Bonen, A; Blewett, C; McDermott, J C; Elder, G C

    1990-07-01

    Nonexercising muscles appear to be metabolically active during exercise. Animal models for this purpose have not been established. However, we have been able to teach animals to run on their forelimbs while their hindlimbs are suspended above the treadmill with no visible limb movement. To document that indeed this mode of exercise does not provoke additional muscle activity, we have compared the levels of neural activation of the soleus and plantaris muscles using a computer analysis of the electromyographic interference pattern, recorded from bipolar fine wire electrodes implanted across each muscle. Via computer analyses of the electromyographic interference patterns the frequencies and amplitudes of motor unit action potentials were obtained. The data were sampled during 20 s of every minute of observation. Comparisons were made in four conditions: (i) resting on the treadmill while bearing weight on the hindlimbs (normal rest), (ii) running on the treadmill (15 m/min, 8% grade) on all four limbs (normal exercise), (iii) resting while the hindlimbs were suspended in a harness above the treadmill (suspended rest), and (iv) exercising with the forelimbs (15 m/min, 8% grade) while the hindlimbs were suspended above the treadmill (suspended exercise). All four experimental conditions were carried out for 90 min each and were performed by each animal. The results clearly show that muscle activities (frequencies and amplitudes), when the hindlimbs are suspended above the treadmill, at rest or during exercise, are lower than the activities in these same muscles when the animals are at rest, supporting only their body weight. Activities in the same muscles during exercise were from 300 to 2000% greater than during hindlimb suspension.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Muscle glucose uptake in the rat after suspension with single hindlimb weight bearing

    NASA Technical Reports Server (NTRS)

    Stump, Craig S.; Woodman, Christopher R.; Fregosi, Ralph F.; Tipton, Charles M.

    1993-01-01

    An examination is conducted of the effect of nonweight-bearing conditions, and the systemic influences of simulated microgravity on rat hindlimb muscles. The results obtained suggest that the increases in hindlimb muscle glucose uptake and extracellular space associated with simulated microgravity persist with hindlimb weightbearing, despite the prevention of muscle atrophy. The mechanism (or mechanisms) responsible for these effects are currently unknown.

  5. Atrophy of the soleus muscle by hindlimb unweighting

    NASA Technical Reports Server (NTRS)

    Thomason, Donald B.; Booth, Frank W.

    1990-01-01

    This paper reviews data derived from the animal hindlimb unweighting model. The review presents the following information about the unweighted soleus muscle: electromyogram activity, the amount and type of protein lost, capillarization, oxidative capacity, glycolytic enzyme activities, fiber cross section, contractile properties, glucose uptake, sensitivity to insulin, the rates of protein synthesis and degradation, the glucocorticoid receptor numbers, the responses of specific mRNAs, and changes in metabolic concentrations. Data of all these studies show that the stress response of the animal to hindlimb suspension is transient and minimal in magnitude (though somewhat variable) and that, after one week of unweighting, the animal exhibits no chronic signs of stress.

  6. Age effects on rat hindlimb muscle atrophy during suspension unloading

    NASA Technical Reports Server (NTRS)

    Steffen, Joseph M.; Fell, Ronald D.; Geoghegan, Thomas E.; Ringel, Lisa C.; Musacchia, X. J.

    1990-01-01

    The effects of hindlimb unloading on muscle mass and biochemical responses were examined and compared in adult (450-g) and juvenile (200-g) rats after 1, 7, or 14 days of whole-body suspension. Quantitatively and qualitatively the soleus, gastrocnemius, plantaris, and extensor digitorum longus (EDL) muscles of the hindlimb exhibited a differential sensitivity to suspension and weightlessness unloading in both adults and juveniles. The red slow-twitch soleus exhibited the most pronounced atrophy under both conditions, with juvenile responses being greater than adult. In contrast, the fast-twitch EDL hypertrophied during suspension and atrophied during weightlessness, with no significant difference between adults and juveniles. Determination of biochemical parameters (total protein, RNA, and DNA) indicates a less rapid rate of response in adult muscles.

  7. Muscle regeneration during hindlimb unloading results in a reduction in muscle size after reloading

    NASA Technical Reports Server (NTRS)

    Mozdziak, P. E.; Pulvermacher, P. M.; Schultz, E.

    2001-01-01

    The hindlimb-unloading model was used to study the ability of muscle injured in a weightless environment to recover after reloading. Satellite cell mitotic activity and DNA unit size were determined in injured and intact soleus muscles from hindlimb-unloaded and age-matched weight-bearing rats at the conclusion of 28 days of hindlimb unloading, 2 wk after reloading, and 9 wk after reloading. The body weights of hindlimb-unloaded rats were significantly (P < 0.05) less than those of weight-bearing rats at the conclusion of hindlimb unloading, but they were the same (P > 0.05) as those of weight-bearing rats 2 and 9 wk after reloading. The soleus muscle weight, soleus muscle weight-to-body weight ratio, myofiber diameter, number of nuclei per millimeter, and DNA unit size were significantly (P < 0.05) smaller for the injured soleus muscles from hindlimb-unloaded rats than for the soleus muscles from weight-bearing rats at each recovery time. Satellite cell mitotic activity was significantly (P < 0.05) higher in the injured soleus muscles from hindlimb-unloaded rats than from weight-bearing rats 2 wk after reloading, but it was the same (P > 0.05) as in the injured soleus muscles from weight-bearing rats 9 wk after reloading. The injured soleus muscles from hindlimb-unloaded rats failed to achieve weight-bearing muscle size 9 wk after reloading, because incomplete compensation for the decrease in myonuclear accretion and DNA unit size expansion occurred during the unloading period.

  8. Hindlimb unloading increases oxidative stress and disrupts antioxidant capacity in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Lawler, John M.; Song, Wook; Demaree, Scott R.; Bloomfield, S. A. (Principal Investigator)

    2003-01-01

    Skeletal muscle disuse with space-flight and ground-based models (e.g., hindlimb unloading) results in dramatic skeletal muscle atrophy and weakness. Pathological conditions that cause muscle wasting (i.e., heart failure, muscular dystrophy, sepsis, COPD, cancer) are characterized by elevated "oxidative stress," where antioxidant defenses are overwhelmed by oxidant production. However, the existence, cellular mechanisms, and ramifications of oxidative stress in skeletal muscle subjected to hindlimb unloading are poorly understood. Thus we examined the effects of hindlimb unloading on hindlimb muscle antioxidant enzymes (e.g., superoxide dismutase, catalase, glutathione peroxidase), nonenzymatic antioxidant scavenging capacity (ASC), total hydroperoxides, and dichlorohydrofluorescein diacetate (DCFH-DA) oxidation, a direct indicator of oxidative stress. Twelve 6 month old Sprague Dawley rats were divided into two groups: 28 d of hindlimb unloading (n = 6) and controls (n = 6). Hindlimb unloading resulted in a small decrease in Mn-superoxide dismutase activity (10.1%) in the soleus muscle, while Cu,Zn-superoxide dismutase increased 71.2%. In contrast, catalase and glutathione peroxidase, antioxidant enzymes that remove hydroperoxides, were significantly reduced in the soleus with hindlimb unloading by 54.5 and 16.1%, respectively. Hindlimb unloading also significantly reduced ASC. Hindlimb unloading increased soleus lipid hydroperoxide levels by 21.6% and hindlimb muscle DCFH-DA oxidation by 162.1%. These results indicate that hindlimb unloading results in a disruption of antioxidant status, elevation of hydroperoxides, and an increase in oxidative stress.

  9. Rat hindlimb muscle responses to suspension hypokinesia/hypodynamia

    NASA Technical Reports Server (NTRS)

    Musacchia, X. J.; Steffen, J. M.; Deavers, D. R.

    1983-01-01

    Hypokinetic/hyupodynamic (H/H) whole body suspension of rats eliminates hindlimb load bearing functions while permitting continued use of the forelimbs. Responses of hindlimb muscles were assessed in terms of absolute and relative weights during 1 and 2 weeks of H/H suspension. Muscle mass loss was in the order soleus greater than gastrocnemius equal to plantaris greater than extensor digitorum longus (EDL). The soleus, a postural antigravity muscle composed mainly of slow twitch fibers, was most sensitive, losing 35 and 45 percent of its weight during the first and second weeks, respectively. The gastrocnemius and plantaris showed losses during the first week but no significant loss during the second wee. The EDL showed little or no weight loss. During post suspension recovery all muscles showed a weight gain. H/H suspended rats failed to grow; following removal from suspension they gained weight linearly, comparable to controls. Products of muscle metabolism including urea, ammonia, and 3-methylhistidine increased in the urine during H/H suspension and were significantly reduced approaching control levels during recovery. This suspension model offers considerable promise for comparison with H/H responses during weightlessness.

  10. (-)-Epicatechin Attenuates Degradation of Mouse Oxidative Muscle Following Hindlimb Suspension.

    PubMed

    Lee, Icksoo; Hüttemann, Maik; Malek, Moh H

    2016-01-01

    The purpose of this study was to conduct a 14-day hindlimb suspension (HS) with and without (-)-epicatechin supplementation to determine whether (-)-epicatechin treatment can attenuate the loss in muscle degradation, angiogenesis, and mitochondrial signaling in oxidative skeletal muscle. Adult mice were randomized into 3 groups: (a) control (C); (b) HS with vehicle (HS-V); and (c) HS with (-)-epicatechin (HS-(-)-Epi). Animals in the HS-(-)-Epi group received (-)-epicatechin (1.0 mg · kg(-1) of body mass) twice daily through oral gavage. For markers related to muscle degradation, the HS-V group had significantly higher protein expression compared with the control and HS-(-)-Epi groups. Moreover, protein expression for myosin heavy chain type I was significantly reduced by approximately 45% in the HS-V group compared with the control and HS-(-)-Epi groups. In addition, capillarity contact and capillary-to-fiber ratio were significantly higher in the HS-(-)-Epi group compared with the HS-V group. Furthermore, protein expression for thrombospondin-1 was significantly higher in HS-V group compared with the control and HS-(-)-Epi groups. Hindlimb suspension also significantly reduced protein expression for mitochondrial signaling compared with the control and HS-(-)-Epi groups. These findings suggest that (-)-epicatechin supplementation attenuates degradation in oxidative muscles after HS.

  11. Muscle moment arms and sensitivity analysis of a mouse hindlimb musculoskeletal model.

    PubMed

    Charles, James P; Cappellari, Ornella; Spence, Andrew J; Wells, Dominic J; Hutchinson, John R

    2016-10-01

    Musculoskeletal modelling has become a valuable tool with which to understand how neural, muscular, skeletal and other tissues are integrated to produce movement. Most musculoskeletal modelling work has to date focused on humans or their close relatives, with few examples of quadrupedal animal limb models. A musculoskeletal model of the mouse hindlimb could have broad utility for questions in medicine, genetics, locomotion and neuroscience. This is due to this species' position as a premier model of human disease, having an array of genetic tools for manipulation of the animal in vivo, and being a small quadruped, a category for which few models exist. Here, the methods used to develop the first three-dimensional (3D) model of a mouse hindlimb and pelvis are described. The model, which represents bones, joints and 39 musculotendon units, was created through a combination of previously gathered muscle architecture data from microdissections, contrast-enhanced micro-computed tomography (CT) scanning and digital segmentation. The model allowed muscle moment arms as well as muscle forces to be estimated for each musculotendon unit throughout a range of joint rotations. Moment arm analysis supported the reliability of musculotendon unit placement within the model, and comparison to a previously published rat hindlimb model further supported the model's reliability. A sensitivity analysis performed on both the force-generating parameters and muscle's attachment points of the model indicated that the maximal isometric muscle moment is generally most sensitive to changes in either tendon slack length or the coordinates of insertion, although the degree to which the moment is affected depends on several factors. This model represents the first step in the creation of a fully dynamic 3D computer model of the mouse hindlimb and pelvis that has application to neuromuscular disease, comparative biomechanics and the neuromechanical basis of movement. Capturing the morphology

  12. The growth patterns of three hindlimb muscles in the chicken.

    PubMed

    Helmi, C; Cracraft, J

    1977-07-01

    This study was designed to investigate the growth patterns of three hindlimb muscles of the chicken relative to the functional-biomechanical demands of increasing body size. The biceps femoris, a bipennate non-postural muscle, grew relatively faster in terms of wet and dry weight than did the parallel-fibred adductor superficialis or the unipennate adductor profundus, both postural muscles. All three muscles exhibited positive allometry (relative to body weight) in muscle length but only biceps femoris and adductor profundus showed positive allometry in cross sectional area adductor superficialis having isometric growth in this parameter. In biceps femoris and adductor superficialis the lengths of the longest and shortest fasciculi grew at equal rates, whereas in adductor profundus the shortest fasciculi grew faster than the longest. We conclude that muscle weight alone is an insufficient indicator of changing function in growing muscle. Hence, growth studies should include other functionally relevant parameters such as cross sectional area, which is proportional to the force-producing capabilities of the muscle, or fibre (fasciculus) length, which is indicative of the absolute amount of stretching or shortening that is possible and of the contraction velocity.

  13. The growth patterns of three hindlimb muscles in the chicken.

    PubMed Central

    Helmi, C; Cracraft, J

    1977-01-01

    This study was designed to investigate the growth patterns of three hindlimb muscles of the chicken relative to the functional-biomechanical demands of increasing body size. The biceps femoris, a bipennate non-postural muscle, grew relatively faster in terms of wet and dry weight than did the parallel-fibred adductor superficialis or the unipennate adductor profundus, both postural muscles. All three muscles exhibited positive allometry (relative to body weight) in muscle length but only biceps femoris and adductor profundus showed positive allometry in cross sectional area adductor superficialis having isometric growth in this parameter. In biceps femoris and adductor superficialis the lengths of the longest and shortest fasciculi grew at equal rates, whereas in adductor profundus the shortest fasciculi grew faster than the longest. We conclude that muscle weight alone is an insufficient indicator of changing function in growing muscle. Hence, growth studies should include other functionally relevant parameters such as cross sectional area, which is proportional to the force-producing capabilities of the muscle, or fibre (fasciculus) length, which is indicative of the absolute amount of stretching or shortening that is possible and of the contraction velocity. PMID:885779

  14. Organization of lumbosacral motoneuronal cell groups innervating hindlimb, pelvic floor, and axial muscles in the cat.

    PubMed

    Vanderhorst, V G; Holstege, G

    1997-05-26

    In a study on descending pathways from the nucleus retroambiguus (NRA) to hindlimb motoneurons (see accompanying paper), it appeared impossible, using data from the literature, to precisely determine which muscles were innervated by the motoneurons receiving the NRA fibers. This lack of data made it necessary to produce a detailed map of the lumbosacral motoneuronal cell groups in the cat. Therefore, 50 different muscles or muscle compartments of hindlimb, pelvic floor and lower back were injected with horseradish peroxidase (HRP) in 135 cases. The respective muscles were divided into ten groups: I, sartorius and iliopsoas; II, quadriceps; III, adductors; IV, hamstrings; V, gluteal and other proximal muscles of the hip; VI, posterior compartment of the distal hindlimb; VII, anterior compartment of the distal hindlimb; VIII, long flexors and intrinsic muscles of the foot; IX, pelvic floor muscles; and X, extensors of the lower back and tail. The L4-S2 segments were cut and incubated, and labeled motoneurons were counted and plotted. A new method was developed that made it possible, despite variations in size and segmental organization between the different cases, to compare the results of different cases. The results show that the spatial interrelationship between the hindlimb and pelvic floor lumbosacral motoneuronal cell groups remains constant. This finding enabled the authors to compose an accurate overall map of the location of lumbosacral motoneuronal cell groups. The general distribution of the motoneuronal cell groups is also discussed in respect to their dorsoventral, mediolateral, and rostrocaudal position within the lumbosacral ventral horn. PMID:9136811

  15. Effects of insulin and exercise on rat hindlimb muscles after simulated microgravity

    NASA Technical Reports Server (NTRS)

    Stump, Craig S.; Balon, Thomas W.; Tipton, Charles M.

    1992-01-01

    The effect of simulated microgravity on the insulin- and exercise-stimulated glucose uptake and metabolism in the hindlimb muscles of rats was investigated using three groups of rats suspended at 45 head-down tilt (SUS) for 14 days: (1) cage control, (2) exercising (treadmill running) control, and (3) rats subjected to suspension followed by exercise (SUS-E). It was found that the suspension of rats with hindlimbs non-weight bearing led to enhanced muscle responses to insulin and exercise, when these stimuli were applied separately. However, the insulin affect appeared to be impaired after exercise for the SUS-E rats, especially for the soleus muscle.

  16. Effects of hypokinesia and hypodynamia upon protein turnover in hindlimb muscles of the rat

    NASA Technical Reports Server (NTRS)

    Loughna, Paul T.; Goldspink, David F.; Goldspink, Geoffrey

    1987-01-01

    Hypokinesia/hypodynamia was induced in the hindlimb muscles of the rat, using a suspension technique. This caused differing degrees of atrophy in different muscles. However, this atrophy was reduced in muscles held in a lenghthened position. The greatest degree of wasting was observed in the unstretched soleus, a slow postural muscle, where both Type 1 and Type 2a fibers atrophied to the same degree. However, wasting of the gastrocnemius muscle was associated with a reduction in the size of the Type 2b fibers. In both slow-postural and fast-phasic hindlimb muscles, atrophy was brought about by a reduction in the rate of protein synthesis in conjunction with an elevation in the rate of protein degradation. When inactive muscles were passively stretched, both protein synthesis and degradation were dramatically elevated. Even periods of stretch of as little as 0.5 h/d were found to significantly decrease atrophy in inactive muscles.

  17. Differences in Age-Related Alterations in Muscle Contraction Properties in Rat Tongue and Hindlimb

    ERIC Educational Resources Information Center

    Connor, Nadine P.; Ota, Fumikazu; Nagai, Hiromi; Russell, John A.; Leverson, Glen

    2008-01-01

    Purpose: Because of differences in muscle architecture and biomechanics, the purpose of this study was to determine whether muscle contractile properties of rat hindlimb and tongue were differentially affected by aging. Method: Deep peroneal and hypoglossal nerves were stimulated in 6 young and 7 old Fischer 344-Brown Norway rats to allow…

  18. Combined effects of botulinum toxin injection and hindlimb unloading on bone and muscle

    PubMed Central

    Ellman, Rachel; Grasso, Daniel J.; van Vliet, Miranda; Brooks, Daniel J.; Spatz, Jordan M.; Conlon, Christine; Bouxsein, Mary L.

    2014-01-01

    Bone receives mechanical stimulation from two primary sources, muscle contractions and external gravitational loading, but the relative contribution of each source to skeletal health is not fully understood. Understanding the most effective loading for maintaining bone health has important clinical implications for prescribing physical activity for the treatment or prevention of osteoporosis. Therefore, we investigated the relative effects of muscle paralysis and reduced gravitational loading on changes in muscle mass, bone mineral density and microarchitecture. Adult female C57Bl/6J mice (n=10/group) underwent one of the following: unilateral botulinum toxin (BTX) injection of the hindlimb, hindlimb unloading (HLU), both unilateral BTX injection and HLU, or no intervention. BTX and HLU each led to significant muscle and bone loss. The effect of BTX was diminished when combined with HLU, though generally the leg that received the combined intervention (HLU + BTX) had the most detrimental changes in bone and muscle. We found an indirect effect of BTX affecting the uninjected (contralateral) leg that led to significant decreases in bone mineral density and deficits in muscle mass and bone architecture relative to the untreated controls; the magnitude of this indirect BTX effect was comparable to the direct effect of BTX treatment and HLU. Thus, while it was difficult to definitively conclude whether muscle forces or external gravitational loading contribute more to bone maintenance, it appears that BTX-induced muscle paralysis is more detrimental to muscle and bone than hindlimb unloading. PMID:24240478

  19. Musculoskeletal Geometry, Muscle Architecture and Functional Specialisations of the Mouse Hindlimb

    PubMed Central

    Charles, James P.; Cappellari, Ornella; Spence, Andrew J.; Hutchinson, John R.; Wells, Dominic J.

    2016-01-01

    Mice are one of the most commonly used laboratory animals, with an extensive array of disease models in existence, including for many neuromuscular diseases. The hindlimb is of particular interest due to several close muscle analogues/homologues to humans and other species. A detailed anatomical study describing the adult morphology is lacking, however. This study describes in detail the musculoskeletal geometry and skeletal muscle architecture of the mouse hindlimb and pelvis, determining the extent to which the muscles are adapted for their function, as inferred from their architecture. Using I2KI enhanced microCT scanning and digital segmentation, it was possible to identify 39 distinct muscles of the hindlimb and pelvis belonging to nine functional groups. The architecture of each of these muscles was determined through microdissections, revealing strong architectural specialisations between the functional groups. The hip extensors and hip adductors showed significantly stronger adaptations towards high contraction velocities and joint control relative to the distal functional groups, which exhibited larger physiological cross sectional areas and longer tendons, adaptations for high force output and elastic energy savings. These results suggest that a proximo-distal gradient in muscle architecture exists in the mouse hindlimb. Such a gradient has been purported to function in aiding locomotor stability and efficiency. The data presented here will be especially valuable to any research with a focus on the architecture or gross anatomy of the mouse hindlimb and pelvis musculature, but also of use to anyone interested in the functional significance of muscle design in relation to quadrupedal locomotion. PMID:27115354

  20. Acute effects of hindlimb unweighting on satellite cells of growing skeletal muscle

    NASA Technical Reports Server (NTRS)

    Schultz, Edward; Darr, Kevin C.; Macius, Allison

    1994-01-01

    The proliferative behavior of satellite cells in growing rat soleus and extensor digitorum longus muscles was examined at short periods after initiation of hindlimb unweighting. Mitotic activity of satellite cells in both muscles decreased below weight-bearing control levels within 24 h of initiation of hindlimb unweighting. This satellite cell response was equal to or greater than 48 h before any atrophic morphological changes that take place in the muscles. Suppression of mitotic activity was most severe in the soleus muscle where continuous infusion of label demonstrated that virtually all mitotic activity was abolished between 3 and 5 days. The results of this study suggest that satellite cell mitotic activity is a sensitive indicator of primary atrophic changes occurring in growing myofibers and may be a predictor of future morphological changes.

  1. Insulin effect on amino acid uptake by unloaded rat hindlimb muscles

    NASA Technical Reports Server (NTRS)

    Jaspers, S. R.; Tischler, M. E.

    1988-01-01

    The effect of insulin on the uptake of alpha-amino-isobutyric acid (AIB) by unloaded rat hindlimb muscles was investigated using soleus and extensor digitorum longus (EDL) muscles from intact and adrenalectomized (ADX) rats that were tail-casted for six days. It was found that, at insulin levels above 0.00001 units/ml, the in vitro rate of AIB uptake by muscles from intact animals was stimulated more in the weight bearing muscles than in unloaded ones. In ADX animals, this differential response to insulin was abolished.

  2. Response of rat hindlimb muscles to 12 hours recovery from tail-cast suspension

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.; Henriksen, E. J.; Jacob, S.; Cook, P.; Jaspers, S.

    1985-01-01

    Previous work has shown a number of biochemical changes which accompany atrophy or reduced muscle growth in hindlimb of tail-casted, suspended rats. These results clearly show that altered muscle growth was due to changes in protein turnover. Accordingly, the rise in soleus tyrosine following unloading reflects the more negative protein balance. Other major changes we found included slower synthesis of glutamine as indicated by lower ratios of glutamine/glutamate and reduced levels of aspartate which coincide with slower aspartate and ammonia metabolism in vitro. In conjunction with the study of SL-3 rats, which were subjected to 12 h of post-flight gravity, a study of the effects of 12 h eight bearing on metabolism of 6-day unloaded hindlimb muscles was carried out.

  3. Intracellular Ca2+ transients in mouse soleus muscle after hindlimb unloading and reloading

    NASA Technical Reports Server (NTRS)

    Ingalls, C. P.; Warren, G. L.; Armstrong, R. B.; Hamilton, S. L. (Principal Investigator)

    1999-01-01

    The objective of this study was to determine whether altered intracellular Ca(2+) handling contributes to the specific force loss in the soleus muscle after unloading and/or subsequent reloading of mouse hindlimbs. Three groups of female ICR mice were studied: 1) unloaded mice (n = 11) that were hindlimb suspended for 14 days, 2) reloaded mice (n = 10) that were returned to their cages for 1 day after 14 days of hindlimb suspension, and 3) control mice (n = 10) that had normal cage activity. Maximum isometric tetanic force (P(o)) was determined in the soleus muscle from the left hindlimb, and resting free cytosolic Ca(2+) concentration ([Ca(2+)](i)), tetanic [Ca(2+)](i), and 4-chloro-m-cresol-induced [Ca(2+)](i) were measured in the contralateral soleus muscle by confocal laser scanning microscopy. Unloading and reloading increased resting [Ca(2+)](i) above control by 36% and 24%, respectively. Although unloading reduced P(o) and specific force by 58% and 24%, respectively, compared with control mice, there was no difference in tetanic [Ca(2+)](i). P(o), specific force, and tetanic [Ca(2+)](i) were reduced by 58%, 23%, and 23%, respectively, in the reloaded animals compared with control mice; however, tetanic [Ca(2+)](i) was not different between unloaded and reloaded mice. These data indicate that although hindlimb suspension results in disturbed intracellular Ca(2+) homeostasis, changes in tetanic [Ca(2+)](i) do not contribute to force deficits. Compared with unloading, 24 h of physiological reloading in the mouse do not result in further changes in maximal strength or tetanic [Ca(2+)](i).

  4. Development of fore- and hindlimb muscles in GFP-transgenic axolotls: morphogenesis, the tetrapod bauplan, and new insights on the forelimb-hindlimb enigma.

    PubMed

    Diogo, Rui; Tanaka, Elly M

    2014-02-01

    The axolotl is becoming one of the most used model organisms in developmental and regenerative studies but no publication has described in detail the development of its forelimb and hindlimb muscles. We describe and illustrate the ontogeny of these muscles in transgenic axolotls that express GFP in muscle fibers and discuss our results and data previously obtained by us and by other authors about limb regeneration in axolotls and ontogeny in frogs and other tetrapods. Our observations and comparisons: (1) demonstrate radio-ulnar and ventro-dorsal morphogenetic gradients in the order of axolotl forelimb muscle formation and differentiation, while in axolotl hindlimb ontogeny there are only proximo-distal and tibio-fibular gradients; some of the axolotl gradients are therefore different from the ulno-radial/fibulo-tibial fore- and hindlimb and the dorso-ventral hindimb ontogenetic morphogenetic gradients seen in frogs and amniotes such as chickens; (2) provide a potential explanation for the usual presence, in both limbs of taxa from all major tetrapod groups, of more radial/tibial muscles than ulnar/fibular muscles; (3) support the "in-out" developmental mechanism of appendicular muscle formation; (4) offer new insights about the ancestral Bauplan of tetrapod limbs, including the striking similarity of the zeugopodial (forearm/leg) and autopodial (hand/foot) muscles of the two limbs and the ventro-dorsal symmetry of the zeugopodial muscles of a same limb; and (5) provide further evidence to corroborate the hypothesis that these similarities are due to derived homoplastic events that occurred during the fins-limbs transition and not due to forelimb-hindlimb serial homology. PMID:24302552

  5. Force-velocity properties of two avian hindlimb muscles.

    PubMed

    Nelson, Frank E; Gabaldón, Annette M; Roberts, Thomas J

    2004-04-01

    Recent work has provided measurements of power output in avian skeletal muscles during running and flying, but little is known about the contractile properties of avian skeletal muscle. We used an in situ preparation to characterize the force-velocity properties of two hind limb muscles, the lateral gastrocnemius (LG) and peroneus longus (PL), in Wild Turkeys (Meleagris gallopavo). A servomotor measured shortening velocity for at least six different loads over the plateau region of the length-tension curve. The Hill equation was fit to the data to determine maximum shortening velocity and peak instantaneous power. Maximum unloaded shortening velocity was 13.0+/-1.6 L s(-1) for the LG muscle and 14.8+/-1.0 L s(-1) for the PL muscle (mean+/-S.E.M.). These velocities are within the range of values published for reptilian and mammalian muscles. Values recorded for maximum isometric force per cross-sectional area, 271+/-28 kPa for the LG and 257+/-30.5 kPa for the PL, and peak instantaneous power output, 341.7+/-36.4 W kg(-1) for the LG and 319.4+/-42.5 W kg(-1) for the PL, were also within the range of published values for vertebrate muscle. The force-velocity properties of turkey LG and PL muscle do not reveal any extreme differences in the mechanical potential between avian and other vertebrate muscle.

  6. Changes in skeletal muscle properties following hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Patterson, G. T.; Dettbarn, W.-D.

    1985-01-01

    Changes in AChE regulation, the functions of the sarcoplasmic reticulum (SR), and muscle fiber-type population in the extensor digitorium longus (EDL) and soleus of male rats suspended in a nonweight-bearing position are studied. Muscle weight, AChE activity, protein content, SR calcium loading rates, and muscle types in the suspended and control rats are evaluated and compared. It is observed that following 1-4 weeks of suspension the EDL is unaffected; however, the soleus muscle weight, and protein content decrease and the AChE activity increases. The SR calcium loading rates of EDL decrease 10 percent and the soleus increase 50 percent in the suspended rats. The data reveal that the population of muscle type 1 (slow fibers) decreases and type 2 (fast fibers) increases for the soleus, and the distribution is unchanged for the EDL of the suspended rats. It is detected that a nonweight-bearing position affects the soleus (a fast-twitch muscle), but not the EDL (a slow-twitch muscle).

  7. Recovery of skeletal muscle after 3 mo of hindlimb immobilization in rats

    NASA Technical Reports Server (NTRS)

    Booth, F. W.; Seider, M. J.

    1979-01-01

    During immobilization, skeletal muscle undergoes decreases in size and strength with concomitant atrophic and degenerative changes in slow-twitch muscle fibers. Currently there are no objective data in slow-twitch muscle demonstrating recovery of biochemical or physiological indices following termination of immobilization. The purpose of this study was to determine whether the soleus, a slow-twitch muscle, could recover normal biochemical or physiological levels following termination of immobilization. Adenosine triphosphate, glycogen, and protein concentration (mg/g wet wt) all significantly decreased following 90 days of hindlimb immobilization, but these three values returned to control levels by the 60th recovery day. Similarly, soleus muscle wet weight and protein content (mg protein/muscle) returned to control levels by the 14th recovery day. In contrast, maximal isometric tension did not return to normal until the 120th day. These results indicate that following muscular atrophy, which was achieved through 90 days of hindlimb immobilization, several biochemical and physiological values in skeletal muscle are recovered at various times after the end of immobilization.

  8. Myosin heavy chain composition of tiger (Panthera tigris) and cheetah (Acinonyx jubatus) hindlimb muscles.

    PubMed

    Hyatt, Jon-Philippe K; Roy, Roland R; Rugg, Stuart; Talmadge, Robert J

    2010-01-01

    Felids have a wide range of locomotor activity patterns and maximal running speeds, including the very fast cheetah (Acinonyx jubatas), the roaming tiger (Panthera tigris), and the relatively sedentary domestic cat (Felis catus). As previous studies have suggested a relationship between the amount and type of activity and the myosin heavy chain (MHC) isoform composition of a muscle, we assessed the MHC isoform composition of selected hindlimb muscles from these three felid species with differing activity regimens. Using gel electrophoresis, western blotting, histochemistry, and immunohistochemistry with MHC isoform-specific antibodies, we compared the MHC composition in the tibialis anterior, medial gastrocnemius (MG), plantaris (Plt), and soleus muscles of the tiger, cheetah, and domestic cat. The soleus muscle was absent in the cheetah. At least one slow (type I) and three fast (types IIa, IIx, and IIb) MHC isoforms were present in the muscles of each felid. The tiger had a high combined percentage of the characteristically slower isoforms (MHCs I and IIa) in the MG (62%) and the Plt (86%), whereas these percentages were relatively low in the MG (44%) and Plt (55%) of the cheetah. In general, the MHC isoform characteristics of the hindlimb muscles matched the daily activity patterns of these felids: the tiger has daily demands for covering long distances, whereas the cheetah has requirements for speed and power.

  9. Effect of hindlimb suspension and clenbuterol treatment on polyamine levels in skeletal muscle

    NASA Technical Reports Server (NTRS)

    Abukhalaf, Imad K.; von Deutsch, Daniel A.; Wineski, Lawrence E.; Silvestrov, Natalia A.; Abera, Saare A.; Sahlu, Sinafikish W.; Potter, David E.; Thierry-Palmer, M. (Principal Investigator)

    2002-01-01

    Polyamines are unbiquitous, naturally occurring small aliphatic, polycationic, endogenous compounds. They are involved in many cellular processes and may serve as secondary or tertiary messengers to hormonal regulation. The relationship of polyamines and skeletal muscle mass of adductor longus, extensor digitorum longus, and gastrocnemius under unloading (hindlimb suspension) conditions was investigated. Unloading significantly affected skeletal muscle polyamine levels in a fiber-type-specific fashion. Under loading conditions, clenbuterol treatment increased all polyamine levels, whereas under unloading conditions, only the spermidine levels were consistently increased. Unloading attenuated the anabolic effects of clenbuterol in predominately slow-twitch muscles (adductor longus), but had little impact on clenbuterol's action as a countermeasure in fast- twitch muscles such as the extensor digitorum longus. Spermidine appeared to be the primary polyamine involved in skeletal muscle atrophy/hypertrophy. Copyright 2002 S. Karger AG, Basel.

  10. Effect of anabolic steroids on skeletal muscle mass during hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Tsika, R. W.; Herrick, R. E.; Baldwin, K. M.

    1987-01-01

    The effect of treatment with an anabolic steroid (nandrolone decanoate) on the muscle mass of plantaris and soleus of a rats in hindlimb suspension, and on the isomyosin expression in these muscles, was investigated in young female rats divided into four groups: normal control (NC), normal steroid (NS), normal suspension (N-sus), and suspension steroid (sus-S). Steroid treatment of suspended animals (sus-S vs N-sus) was found to partially spare body weight and muscle weight, as well as myofibril content of plantaris (but not soleus), but did not modify the isomyosin pattern induced by suspension. In normal rats (NS vs NC), steroid treatment did enhance body weight and plantaris muscle weight; the treatment did not alter isomyosin expression in either muscle type.

  11. Defective excitation-contraction coupling is partially responsible for impaired contractility in hindlimb muscles of Stac3 knockout mice

    PubMed Central

    Cong, Xiaofei; Doering, Jonathan; Grange, Robert W.; Jiang, Honglin

    2016-01-01

    The Stac3 gene is exclusively expressed in skeletal muscle, and Stac3 knockout is perinatal lethal in mice. Previous data from Stac3-deleted diaphragms indicated that Stac3-deleted skeletal muscle could not contract because of defective excitation-contraction (EC) coupling. In this study, we determined the contractility of Stac3-deleted hindlimb muscle. In response to frequent electrostimulation, Stac3-deleted hindlimb muscle contracted but the maximal tension generated was only 20% of that in control (wild type or heterozygous) muscle (P < 0.05). In response to high [K+], caffeine, and 4-chloro-m-cresol (4-CMC), the maximal tensions generated in Stac3-deleted muscle were 29% (P < 0.05), 58% (P = 0.08), and 55% (P < 0.05) of those in control muscle, respectively. In response to 4-CMC or caffeine, over 90% of myotubes formed from control myoblasts contracted, but only 60% of myotubes formed from Stac3-deleted myoblasts contracted (P = 0.05). However, in response to 4-CMC or caffeine, similar increases in intracellular calcium concentration were observed in Stac3-deleted and control myotubes. Gene expression and histological analyses revealed that Stac3-deleted hindlimb muscle contained more slow type-like fibers than control muscle. These data together confirm a critical role of STAC3 in EC coupling but also suggest that STAC3 may have additional functions in skeletal muscle, at least in the hindlimb muscle. PMID:27184118

  12. Time course changes in [Ca2+]i, force, and protein content in hindlimb-suspended mouse soleus muscles

    NASA Technical Reports Server (NTRS)

    Ingalls, C. P.; Wenke, J. C.; Armstrong, R. B.; Hamilton, S. L. (Principal Investigator)

    2001-01-01

    BACKGROUND: Exposure to reduced gravitational forces during spaceflight is associated with significant reductions in skeletal muscle mass and strength. The purpose of this study was to test the hypothesis that increases in resting cytosolic free calcium concentration ([Ca2+]i) would precede reductions in protein content and maximal isometric tetanic force (Po) in mouse soleus muscle after initiation of hindlimb suspension. METHODS: Female ICR mice (n = 42) were hindlimb suspended for 1, 2, 3, 5, or 7 d; weight-matched mice were used as controls. Following the hindlimb suspension, the left soleus muscle was used to determine Po in vitro and the right soleus muscle was used to determine protein content and [Ca2+]i via confocal laser scanning microscopy. RESULTS: Compared with controls, [Ca2+]i was elevated by 38% at 2 d, and 117% at 7 d. Compared with controls, soleus muscle total and myofibrillar protein contents were reduced 27-29% and 30-34%, respectively, at 5-7 d after initiation of hindlimb suspension. Compared with controls, soleus muscle Po was decreased by 24% at 3 d, and 38% at 7 d. CONCLUSION: It appears that resting cytosolic Ca2+ homeostasis is disturbed soon after the initiation of hindlimb suspension, and these elevations in [Ca2+]i may play a role in initiating soleus muscle atrophy.

  13. A Mathematical Model of Oxygen Transport in Skeletal Muscle During Hindlimb Unloading

    NASA Technical Reports Server (NTRS)

    Causey, Laura; Lewandowski, Beth E.; Weinbaum, Sheldon

    2014-01-01

    During hindlimb unloading (HU) dramatic fluid shifts occur within minutes of the suspension, leading to a less precise matching of blood flow to O2 demands of skeletal muscle. Vascular resistance directs blood away from certain muscles, such as the soleus (SOL). The muscle volume gradually reduces in these muscles so that eventually the relative blood flow returns to normal. It is generally believed that muscle volume change is not due to O2 depletion, but a consequence of disuse. However, the volume of the unloaded rat muscle declines over the course of weeks, whereas the redistribution of blood flow occurs immediately. Using a Krogh Cylinder Model, the distribution of O2 was predicted in two skeletal muscles: SOL and gastrocnemius (GAS). Effects of the muscle blood flow, volume, capillary density, and O2 uptake, are included to calculate the pO2 at rest and after 10 min and 15 days of unloading. The model predicts that 32 percent of the SOL muscle tissue has a pO2 1.25 mm Hg within 10 min, whereas the GAS maintains normal O2 levels, and that equilibrium is reached only as the SOL muscle cells degenerate. The results provide evidence that there is an inadequate O2 supply to the mitochondria in the SOL muscle after 10 min HU.

  14. Effect of seven days of spaceflight on hindlimb muscle protein, RNA and DNA in adult rats

    NASA Technical Reports Server (NTRS)

    Steffen, J. M.; Musacchia, X. J.

    1985-01-01

    Effects of seven days of spaceflight on skeletal muscle (soleus, gastrocnemius, EDL) content of protein, RNA and DNA were determined in adult rats. Whereas total protein contents were reduced in parallel with muscle weights, myofibrillar protein appeared to be more affected. There were no significant changes in absolute DNA contents, but a significant (P less than 0.05) increase in DNA concentration (microgram/milligram) in soleus muscles from flight rats. Absolute RNA contents were significantly (P less than 0.025) decreased in the soleus and gastrocnemius muscles of flight rats, with RNA concentrations reduced 15-30 percent. These results agree with previous ground-based observations on the suspended rat with unloaded hindlimbs and support continued use of this model.

  15. Hindlimb unloading induces a collagen isoform shift in the soleus muscle of the rat

    NASA Technical Reports Server (NTRS)

    Miller, T. A.; Lesniewski, L. A.; Muller-Delp, J. M.; Majors, A. K.; Scalise, D.; Delp, M. D.

    2001-01-01

    To determine whether hindlimb unloading (HU) alters the extracellular matrix of skeletal muscle, male Sprague-Dawley rats were subjected to 0 (n = 11), 1 (n = 11), 14 (n = 13), or 28 (n = 11) days of unloading. Remodeling of the soleus and plantaris muscles was examined biochemically for collagen abundance via measurement of hydroxyproline, and the percentage of cross-sectional area of collagen was determined histologically with picrosirius red staining. Total hydroxyproline content in the soleus and plantaris muscles was unaltered by HU at any time point. However, the relative proportions of type I collagen in the soleus muscle decreased relative to control (Con) with 14 and 28 days HU (Con 68 +/- 5%; 14 days HU 53 +/- 4%; 28 days HU 53 +/- 7%). Correspondingly, type III collagen increased in soleus muscle with 14 and 28 days HU (Con 32 +/- 5%; 14 days HU 47 +/- 4%; 28 days HU 48 +/- 7%). The proportion of type I muscle fibers in soleus muscle was diminished with HU (Con 96 +/- 2%; 14 days HU 86 +/- 1%; 28 days HU 83 +/- 1%), and the proportion of hybrid type I/IIB fibers increased (Con 0%; 14 days HU 8 +/- 2%; 28 days HU 14 +/- 2%). HU had no effect on the proportion of type I and III collagen or muscle fiber composition in plantaris muscle. The data demonstrate that HU induces a shift in the relative proportion of collagen isoform (type I to III) in the antigravity soleus muscle, which occurs concomitantly with a slow-to-fast myofiber transformation.

  16. Atrophy and growth failure of rat hindlimb muscles in tail-cast suspension

    NASA Technical Reports Server (NTRS)

    Jaspers, S. R.; Tischler, M. E.

    1984-01-01

    The primary objective of the present study is related to an evaluation of a modified tail-cast suspension model as a means of identifying metabolic factors which control or are associated with muscle atrophy and growth failure. Two different control conditions (normal and tail-casted weight bearing) were studied to determine the appropriate control for tail-cast suspension. A description is presented of a model which is most useful for studying atrophy of hindlimb muscles under certain conditions. Female Sprague-Dawley rats were employed in the experiments. Attention is given to growth rate and urinary excretion of urea and ammonia in different types of rats, the relationship between body weight and skeletal muscle weight, and the relationship between animal body weight and rates of protein synthesis and protein degradation.

  17. The mechanical actions of muscles predict the direction of muscle activation during postural perturbations in the cat hindlimb.

    PubMed

    Honeycutt, Claire F; Nichols, T Richard

    2014-03-01

    Humans and cats respond to balance challenges, delivered via horizontal support surface perturbations, with directionally selective muscle recruitment and constrained ground reaction forces. It has been suggested that this postural strategy arises from an interaction of limb biomechanics and proprioceptive networks in the spinal cord. A critical experimental validation of this hypothesis is to test the prediction that the principal directions of muscular activation oppose the directions responding muscles exert their forces on the environment. Therefore, our objective was to quantify the endpoint forces of a diverse set of cat hindlimb muscles and compare them with the directionally sensitive muscle activation patterns generated in the intact and decerebrate cat. We hypothesized that muscles are activated based on their mechanical advantage. Our primary expectation was that the principal direction of muscle activation during postural perturbations will be directed oppositely (180°) from the muscle endpoint ground reaction force. We found that muscle activation during postural perturbations was indeed directed oppositely to the endpoint reaction forces of that muscle. These observations indicate that muscle recruitment during balance challenges is driven, at least in part, by limb architecture. This suggests that sensory sources that provide feedback about the mechanical environment of the limb are likely important to appropriate and effective responses during balance challenges. Finally, we extended the analysis to three dimensions and different stance widths, laying the groundwork for a more comprehensive study of postural regulation than was possible with measurements confined to the horizontal plane and a single stance configuration.

  18. Hindlimb unloading-induced muscle atrophy and phenotype transition is attenuated in Smad3+/- mice

    NASA Astrophysics Data System (ADS)

    Chen, X. P.; Zhang, P.; Liu, S. H.; Wang, F.; Ge, X.; Wu, Y.; Fan, M.

    Currently it has been well defined that the microgravity-induced muscle disuse characterized by atrophy and slow-to-fast phenotype transition of the postural muscles such as soleus muscle but the basic mechanism underlying the atrophy and phenotype transition of soleus muscle is still unclear To investigate the developmental mechanisms of muscle atrophy and its phenotype transition under microgravity the soleus muscle of Smad3 and Smad3 - mice after 14 days hindlimb unloading was examined Using histology and immunohistochemistry assay we found that the soleus muscle volume and fiber number appeared a remarkable increases in Smad3 - mice compared to those in Smad3 control In addition Western blot analysis showed that the expression level of myosin heavy chain MHC -slow myofiber specific protein in soleus muscle was visibly higher in Smad3 - mice than in Smad3 mice In contrast the expression level of MHC-fast myofiber specific protein in soleus muscle was visibly lower in Smad3 - mice than in Smad3 mice Furthermore RT-PCR revealed that the expression of Smad3 and myogenic regulatory factor MRF mRNA was inversely regulated Finally we determined that either Smad3 mRNA or Smad3 protein were selectively distributed in quiescent satellite cells in vivo and in reserve cells in vitro Therefore our findings suggested that Smad3 might be a key transcriptional factor for soleus muscle atrophy and slow-to-fast phenotype transition of the slow muscle under microgravity In the future an agent that regulates Smad3 expression may be used to prevent

  19. Apoptosis: a mechanism contributing to remodeling of skeletal muscle in response to hindlimb unweighting

    NASA Technical Reports Server (NTRS)

    Allen, D. L.; Linderman, J. K.; Roy, R. R.; Bigbee, A. J.; Grindeland, R. E.; Mukku, V.; Edgerton, V. R.

    1997-01-01

    The role of apoptosis in the elimination of myonuclei during hindlimb unloading-induced atrophy and the inhibition of apoptosis in the prevention of muscle atrophy were examined. The number of nuclei demonstrating double-stranded DNA fragmentation seen by terminal deoxynucleotidyl transferase (TDT) histochemical staining, an indicator of apoptosis, was significantly increased after 14 days of suspension. Double staining with TDT and antilaminin immunohistochemistry revealed that some TDT-positive nuclei were within the fiber lamina and were most likely myonuclei. The number of fibers containing morphologically abnormal nuclei was also significantly greater in suspended compared with control rats. Combined treatment with growth hormone and insulin-like growth factor I (GH/ IGF-I) and resistance exercise attenuated the increase in TDT-positive nuclei (approximately 26%, P > 0.05) and significantly decreased the number of fibers with morphologically abnormal nuclei. The data suggest that 1) "programmed nuclear death" contributes to the elimination of myonuclei and/or satellite cells from atrophying fibers, and 2) GH/IGF-I administration plus muscle loading ameliorates the apoptosis associated with hindlimb unloading.

  20. Unexpected motor patterns for hindlimb muscles during slope walking in the cat.

    PubMed

    Smith, J L; Carlson-Kuhta, P

    1995-11-01

    1. Hindlimb kinematics and motor patterns were assessed from high-speed ciné film synchronized with electromyographic (EMG) data from cats trained to walk on a walkway placed at four grades (25, 50, 75, and 100%). 2. Flexor muscles of the hip (iliopsoas) and ankle (tibialis anterior) had similar activity patterns for the swing phase of up- and down-slope walking; both flexor muscles also had stance-related activity during down-slope walking and this was unexpected. Extensor muscles of the hip (anterior biceps femoris and anterior semimembranosus), knee [vastus lateralis (VL)], and ankle [lateral gastrocnemius (LG)] were active during the stance phase of up-slope walking. The VL and LG activity was reduced in duration during stance of down-slope walking and centered around paw contact. Hip extensors, however, were totally inactive during stance of down-slope walking, and this was not expected. 3. Flexor muscles at the hip and ankle (not extensor muscles) dominated the stance phase of down-slope walking, especially at the steeper slopes. This switch in motor patterns may be required to counterbalance external forces that produced extension at the hip and ankle joints during the stance phase of down-slope walking. Neural mechanisms for programming stance-related activity of flexor muscles are discussed.

  1. Hindlimb muscle fibre size and glycogen stores in bank voles with increased aerobic exercise metabolism.

    PubMed

    Jaromin, Ewa; Wyszkowska, Julia; Labecka, Anna Maria; Sadowska, Edyta Teresa; Koteja, Paweł

    2016-02-01

    To test hypotheses concerning physiological factors limiting the rate of aerobic exercise metabolism, we used a unique experimental evolution model: lines of bank voles selected for high swim-induced aerobic metabolism (A) and unselected, control lines (C). We investigated putative adaptations that result in the increased performance of the hindlimb muscle (gastrocnemius joined with plantaris). The body mass-adjusted muscle mass was higher in A-lines (0.093 g) than in C-lines (0.083 g; P=0.01). However, selection did not affect mean muscle fibre cross-sectional area (P=0.34) or glycogen content assessed with a histochemical periodic acid-Schiff reaction (PAS; P=0.82). The results suggest that the increased aerobic performance is achieved by an increase of total muscle mass, without major qualitative changes in the muscle fibre architecture. However, such a conclusion should be treated with caution, because other modifications, such as increased density of capillaries or mitochondria, could occur. PMID:26685167

  2. Effects of Microgravity On Oxidative and Antioxidant Enzymes In Mouse Hindlimb Muscle

    NASA Technical Reports Server (NTRS)

    Girten, B.; Hoopes, R.; Steele, M.; Morony, S.; Bateman, T. A.; Sun, S. (Technical Monitor)

    2002-01-01

    Gastrocnemius muscle of mice were analyzed in order to examine the effects of 12 days of microgravity on the oxidative enzyme climate synthase (CS) and the antioxidant enzyme superoxide dismutase (SOD). The female C57BL/6J mice utilized for this study were part of the Commercial Biomedical Testing Module (CBTM) payload that flew aboard STS-108. Mice were housed in Animal Enclosure Modules (AEMs) provided by NASA Ames. The flight (FLT) group and the ground control (CON) group each had 12 mice per group. The AEMs that held the CON group operated on a 48-hour delay from the FLT group and were located inside the Orbital Environmental Simulator (OES) at Kennedy Space Center. The temperature, CO2 and relative humidity inside the OES was regulated based on downlinked information from the shuttle middeck. Student T tests were used to compare groups and a p < 0.05 was used to determine statistical significance. Results indicated that CS levels for the FLT group were significantly lower than the CON group while the SOD levels were significantly higher. The CS FLT mean was 19% lower and the SOD FLT mean was 17% higher than the respective CON group means. Although these findings are among the first muscle enzyme values reported for mice from a shuttle mission, these results are similar to some results previously reported for rats exposed to microgravity or hindlimb suspension. The changes seen during the CBTM payload are reflective of the deconditioning that takes place with disuse of the hindlimbs and indicate that muscle enzyme changes induced by disuse deconditioning are similar in both rodent species.

  3. How spinalized rats can walk: biomechanics, cortex and hindlimb muscle scaling – implications for rehabilitation

    PubMed Central

    Giszter, Simon F; Hockensmith, Greg; Ramakrishnan, Arun; Udoekwere, Ubong Ime

    2011-01-01

    Neonatal spinalized (NST) rats can achieve autonomous weight supported locomotion never seen after adult injury. Mechanisms that support function in NST rats include increased importance of cortical trunk control, and altered biomechanical control strategies for stance and locomotion. Hindlimbs are isolated from perturbations in quiet stance and act in opposition to forelimbs in locomotion in NST rats. Control of roll and yaw of the hindlimbs is crucial in their locomotion. The biomechanics of the hind limbs of NST rats are also likely crucial. We present new data showing the whole leg musculature scales proportional to normal rat musculature in NST rats, regardless of function. This scaling is a prerequisite for the NST rats to most effectively use pattern generation mechanisms and motor patterns that are similar to those present in intact rats. Pattern generation may be built into the lumbar spinal cord by evolution and matched to the limb biomechanics, so preserved muscle scaling may be essential to the NST function observed. PMID:20536943

  4. Is salamander hindlimb regeneration similar to that of the forelimb? Anatomical and morphogenetic analysis of hindlimb muscle regeneration in GFP-transgenic axolotls as a basis for regenerative and developmental studies.

    PubMed

    Diogo, R; Murawala, P; Tanaka, E M

    2014-04-01

    The axolotl Ambystoma mexicanum is one of the most used model organisms in developmental and regenerative studies because it is commonly said that it can reconstitute a normal and fully functional forelimb/hindlimb after amputation. However, there is not a publication that has described in detail the regeneration of the axolotl hindlimb muscles. Here we describe and illustrate, for the first time, the regeneration of the thigh, leg and foot muscles in transgenic axolotls that express green fluorescent protein in muscle fibers and compare our results with data obtained by us and by other authors about axolotl forelimb regeneration and about fore- and hindlimb ontogeny in axolotls, frogs and other tetrapods. Our observations and comparisons point out that: (1) there are no muscle anomalies in any regenerated axolotl hindlimbs, in clear contrast to our previous study of axolotl forelimb regeneration, where we found muscle anomalies in 43% of the regenerated forelimbs; (2) during axolotl hindlimb regeneration there is a proximo-distal and a tibio-fibular morphogenetic gradient in the order of muscle regeneration and differentiation, but not a ventro-dorsal gradient, whereas our previous studies showed that in axolotl forelimb muscle regeneration there are proximo-distal, radio-ulnar and ventro-dorsal morphogenetic gradients. We discuss the broader implications of these observations for regenerative, evolutionary, developmental and morphogenetic studies.

  5. Is salamander hindlimb regeneration similar to that of the forelimb? Anatomical and morphogenetic analysis of hindlimb muscle regeneration in GFP-transgenic axolotls as a basis for regenerative and developmental studies.

    PubMed

    Diogo, R; Murawala, P; Tanaka, E M

    2014-04-01

    The axolotl Ambystoma mexicanum is one of the most used model organisms in developmental and regenerative studies because it is commonly said that it can reconstitute a normal and fully functional forelimb/hindlimb after amputation. However, there is not a publication that has described in detail the regeneration of the axolotl hindlimb muscles. Here we describe and illustrate, for the first time, the regeneration of the thigh, leg and foot muscles in transgenic axolotls that express green fluorescent protein in muscle fibers and compare our results with data obtained by us and by other authors about axolotl forelimb regeneration and about fore- and hindlimb ontogeny in axolotls, frogs and other tetrapods. Our observations and comparisons point out that: (1) there are no muscle anomalies in any regenerated axolotl hindlimbs, in clear contrast to our previous study of axolotl forelimb regeneration, where we found muscle anomalies in 43% of the regenerated forelimbs; (2) during axolotl hindlimb regeneration there is a proximo-distal and a tibio-fibular morphogenetic gradient in the order of muscle regeneration and differentiation, but not a ventro-dorsal gradient, whereas our previous studies showed that in axolotl forelimb muscle regeneration there are proximo-distal, radio-ulnar and ventro-dorsal morphogenetic gradients. We discuss the broader implications of these observations for regenerative, evolutionary, developmental and morphogenetic studies. PMID:24325444

  6. FES control of isometric forces in the rat hindlimb using many muscles.

    PubMed

    Jarc, Anthony M; Berniker, Max; Tresch, Matthew C

    2013-05-01

    Functional electrical stimulation (FES) attempts to restore motor behaviors to paralyzed limbs by electrically stimulating nerves and/or muscles. This restoration of behavior requires specifying commands to a large number of muscles, each making an independent contribution to the ongoing behavior. Efforts to develop FES systems in humans have generally been limited to preprogrammed, fixed muscle activation patterns. The development and evaluation of more sophisticated FES control strategies is difficult to accomplish in humans, mainly because of the limited access of patients for FES experiments. Here, we developed an in vivo FES test platform using a rat model that is capable of using many muscles for control and that can therefore be used to evaluate potential strategies for developing flexible FES control strategies. We first validated this FES test platform by showing consistent force responses to repeated stimulation, monotonically increasing muscle recruitment with constant force directions, and linear summation of costimulated muscles. These results demonstrate that we are able to differentially control the activation of many muscles, despite the small size of the rat hindlimb. We then demonstrate the utility of this platform to test potential FES control strategies, using it to test our ability to effectively produce open-loop control of isometric forces. We show that we are able to use this preparation to produce a range of endpoint forces flexibly and with good accuracy. We suggest that this platform will aid in FES controller design, development, and evaluation, thus accelerating the development of effective FES applications for the restoration of movement in paralyzed patients.

  7. FES control of isometric forces in the rat hindlimb using many muscles.

    PubMed

    Jarc, Anthony M; Berniker, Max; Tresch, Matthew C

    2013-05-01

    Functional electrical stimulation (FES) attempts to restore motor behaviors to paralyzed limbs by electrically stimulating nerves and/or muscles. This restoration of behavior requires specifying commands to a large number of muscles, each making an independent contribution to the ongoing behavior. Efforts to develop FES systems in humans have generally been limited to preprogrammed, fixed muscle activation patterns. The development and evaluation of more sophisticated FES control strategies is difficult to accomplish in humans, mainly because of the limited access of patients for FES experiments. Here, we developed an in vivo FES test platform using a rat model that is capable of using many muscles for control and that can therefore be used to evaluate potential strategies for developing flexible FES control strategies. We first validated this FES test platform by showing consistent force responses to repeated stimulation, monotonically increasing muscle recruitment with constant force directions, and linear summation of costimulated muscles. These results demonstrate that we are able to differentially control the activation of many muscles, despite the small size of the rat hindlimb. We then demonstrate the utility of this platform to test potential FES control strategies, using it to test our ability to effectively produce open-loop control of isometric forces. We show that we are able to use this preparation to produce a range of endpoint forces flexibly and with good accuracy. We suggest that this platform will aid in FES controller design, development, and evaluation, thus accelerating the development of effective FES applications for the restoration of movement in paralyzed patients. PMID:23303688

  8. Physiological properties of tandem muscle spindles in neck and hind-limb muscles.

    PubMed

    Price, R F; Dutia, M B

    1989-01-01

    Although tandem muscle spindle complexes are found in small but significant numbers in most muscles, experimental investigation of their properties has been problematic because of the difficulty of distinguishing their afferents from those of "normal" single spindles. Of particular interest are the afferents from b2c capsules of tandem spindles, which unlike normal spindles contain only a static b2 nuclear bag fibre and some nuclear chain fibres. The absence of a dynamic b1 nuclear bag fibre from b2c spindles has engendered much speculation as to their response properties and their possible role in motor control. We have recently developed a method for the identification of afferents from b2c spindles in electrophysiological experiments, using infusion or topical application of succinylcholine (SCh). SCh causes the contraction of the dynamic b1 and static b2 nuclear bag intrafusal fibres, and paralyses the nuclear chain fibres. Afferents from b2c spindles are characterized by a strong "biasing" of their discharge rate to about 100 impulses per second (i.p.s.) when activated by SCh (reflecting the contraction of the static b2 fibre), while primary afferents from normal b1b2c spindles show a large increase in dynamic sensitivity as well as "biasing" (reflecting the contraction of both dynamic b1 and static b2 bag fibres). Histological examination of tenuissimus spindles activated by SCh has confirmed this relationship between the pattern of activation by SCh and the number of intrafusal nuclear bag fibres in the spindle. In this paper we review the value of SCh as a means of testing spindle afferents for functional inputs from sensory terminals on the nuclear bag fibres, and discuss the properties of b2c afferents from tandem spindles in the context of their possible function.

  9. The Effects of Ligustrazine on the Ca2+ Concentration of Soleus and Gastrocnemius Muscle Fibers in Hindlimb Unloaded Rat

    NASA Astrophysics Data System (ADS)

    Gao, Yunfang; Goswami, Nandu; Du, Bei; Hu, Huanxin; Wu, Xue

    Background:Spaceflight or inactivity (bed rest, limb immobilization, hindlimb unloading) causes skeletal muscle atrophy. Recent studies show that an increase in protein degradation is an important mechanism for disuse atrophy. Furthermore, the calcium overload of disuse-atrophied muscle fiber has been shown to initiate the skeletal muscle proteolysis in disuse atrophy. Ligustrazine (tetramethylpyrazine, TMP), one of the important active ingredient extracted from Chuanxiong, has been shown by our group to increase muscle fiber cross-sectional area in atrophied soleus induced by 14 days hindlimb unloading. However, the underlying mechanisms of ligustrazine effects on disuse-atrophied muscle fibers remain unknown. Objective: We investigated the effects of ligustrazine on the cytoplasmic calcium overloading in soleus and gastrocnemius in 14 days hindlimb unloaded (HU) rats. Methods: Adult female Sprague-Dawley rats were matched for body mass and randomly assigned to three groups (n=8, each group): 1) synchronous control (CON); HU + intragastric water instillation (HU+W); HU + intragastric 60.0 mg kg-1 ligustrazine instillation (HU+Tmp). Laser scanning confocal microscope assessed the concentrations of cytoplasmic calcium ions. Spaceflight disuse atrophy was simulated by hindlimb unloading, provided by tail suspension. Results: 1) Compared with CON, the concentration of soleus intracellular calcium ion in HU+W and HU+Tmp increased 330% and 86% respectively(P<0.01). Compared with HU+W, the concentration of soleus intracellular calcium ion in HU+Tmp decreased by 130%(P<0.01). 2) Compared with CON, the concentration of gastrocnemius intracellular calcium ion in HU+W and HU+Tmp increased 189.8% and 32.1% respectively(P<0.01). Compared with HU+W, the concentration of gastrocnemius intracellular calcium ion in HU+Tmp decreased by 119.3% (P<0.01). Conclusion: After 14 days of hindlimb unloading, cytoplasmic calcium of soleus (slow-twitch muscle) and gastrocnemius (fast

  10. Effect of recovery mode following hind-limb suspension on soleus muscle composition in the rat

    NASA Technical Reports Server (NTRS)

    McNulty, A. L.; Otto, A. J.; Kasper, C. E.; Thomas, D. P.

    1992-01-01

    The purpose of this study was to compare the effects of two different recovery modes from hind-limb suspension-induced hypodynamia on whole body and muscle (soleus) growth as well as soleus composition and size changes of different fiber types within this same muscle. Following 28 days of tail-suspension, rats were returned to their cages and sedentarily recovered (HS), or were exercised by running on a treadmill 5 days/wk, at progressively increasing workloads (HR) for one month. Sedentary and running control groups of animals (CS, CR) were also evaluated for comparative purposes. The exercise program, which was identical for CR and HR groups, had no effect on body wt., soleus wt., soleus muscle composition or fiber size in CR rats. Atrophied soleus muscle and reduced soleus wt./body wt. ratio (both 60% of control) had returned to control values by day 7 of recovery in both suspended groups despite the fact that whole body wt. gain was significantly reduced (p less than 0.05) in HR as compared to HS rats. Atrophied soleus Type I fiber mean cross-sectional area in both HR and HS groups demonstrated similar and significant (p less than 0.01) increases during recovery. Increases in Type IIa and IIc fiber area during this same period were significant only in the HR group. While the percentage area of muscle composed of Type I fibers increased in both hypodynamic groups during recovery, the reduction in area percentage of muscle made up of Type IIa fibers was again only significant in the HR group.(ABSTRACT TRUNCATED AT 250 WORDS).

  11. Influence of 7 days of hindlimb suspension and intermittent weight support on rat muscle mechanical properties

    NASA Technical Reports Server (NTRS)

    Pierotti, David J.; Roy, Roland R.; Flores, Vinicio; Edgerton, Reggie

    1990-01-01

    The effect of intermittent periods of weight support on a decrease in mass of the soleus (Sol) and medial gastrocnemius (MG) muscles atrophied by hindlimb suspension (HS) was investigated in rats subjected to continuous HS for seven days or an HS plus intermittent (10 min every 6 hrs of slow walking on a treadmill) weight support (HS-WS). After 7 d HS, the Sol weight relative to body weight was 21 and 9 percent lower in Hs and HS-WS, respectively, than in control rats. Maximum tetanic tension/muscle mass ratio was significantly lower in HS than in controls; the HS-WS rats had values similar to controls, whereas the maximum tetanic tension/muscle weight was significantly elevated in HS-WS compared to controls. Contraction times were 25 percent faster in the Sol and unchanged in the MG of HS rats, indicating that a low-force short-duration exercise regime results in a significant functional recovery in the 'slow' Sol, whereas the 'fast' MG is less affected.

  12. Response of amino acids in hindlimb muscles to recovery from hypogravity and unloading by tail-cast suspension

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.; Henriksen, E. J.; Jacob, S.; Cook, P. H.

    1985-01-01

    Concentrations of glutamine, glutamate, aspartate (+ asparagine) and alanine were compared in hindlimb muscles of SL-3 and ground control rats. Alanine was lower in the soleus of flown rats but not of suspended animals, with no response in other muscles except a slight increase in the unloaded plantaris. With recovery, alanine in the soleus was elevated. Since no differences in alanine metabolism were found by isolated muscle, changes in muscle alanine are probably due to altered body use of this amino acid leading to varied plasma levels.

  13. Patterns of fusimotor activity during locomotion in the decerebrate cat deduced from recordings from hindlimb muscle spindles.

    PubMed

    Taylor, A; Durbaba, R; Ellaway, P H; Rawlinson, S

    2000-02-01

    1. Recordings have been made from multiple single muscle spindle afferents from medial gastrocnemius (MG) and tibialis anterior (TA) muscles of one hindlimb in decerebrate cats, together with ankle rotation and EMG signals, during treadmill locomotion. Whilst the other three limbs walked freely, the experimental limb was denervated except for the nerves to MG and TA and secured so that it could rotate only at the ankle joint, without any external load. Each afferent was characterised by succinylcholine testing with regard to its intrafusal fibre contacts. Active movements were recorded and then replayed through a servo mechanism to reproduce the muscle length changes passively after using a barbiturate to suppress gamma-motor firing. 2. The difference in secondary afferent firing obtained by subtracting the discharge during passive movements from that during active movements was taken to represent the profile of static fusimotor activity. This indicated an increase before the onset of movement followed by a strongly modulated discharge in parallel with muscle shortening during locomotion. The pattern of static firing matched the pattern of unloaded muscle shortening very closely in the case of TA and with some phase advance in the case of MG. The same effects were observed in primary afferents. 3. Primary afferents with bag1 (b1) contacts in addition showed higher firing frequencies during muscle lengthening in active than in passive movements. This indicated increased dynamic fusimotor firing during active locomotion. There was no evidence as to whether this fluctuated during the movement cycles. 4. When the mean active minus passive difference profile of firing in bag2-chain (b2c) type primary afferents was subtracted from that for b1b2c afferents, the difference was dominated by a peak centred on the moment of maximum lengthening velocity (v). 5. The component of the active minus passive difference firing due to b1 fibre contacts could be modelled by f(t) = av

  14. Comparative functional anatomy of hindlimb muscles and bones with reference to aquatic adaptation of the sea otter

    PubMed Central

    MORI, Kent; SUZUKI, Satoshi; KOYABU, Daisuke; KIMURA, Junpei; HAN, Sung-Yong; ENDO, Hideki

    2015-01-01

    Although the sea otter (Enhydra lutris) is a complete aquatic species, spending its entire life in the ocean, it has been considered morphologically to be a semi-aquatic animal. This study aimed to clarify the unique hindlimb morphology and functional adaptations of E. lutris in comparison to other Mustelidae species. We compared muscle mass and bone measurements of five Mustelidae species: the sea otter, Eurasian river otter (Lutra lutra), American mink (Neovison vison), Japanese weasel (Mustela itatsi) and Siberian weasel (M. sibirica). In comparison with the other 4 species, E. lutris possessed significantly larger gluteus, popliteus and peroneus muscles, but smaller adductor and ischiopubic muscles. The popliteus muscle may act as a medial rotator of the crus, and the peroneus muscle may act as an abductor of the fifth toe and/or the pronator of the foot. The bundles of the gluteus superficialis muscle of E. lutris were fused with those of the tensor fasciae latae muscle and gluteofemoralis muscles, and they may play a role in femur abduction. These results suggest that E. lutris uses the abducted femur, medially rotated crus, eversion of the ankle and abducted fifth digit or extended interdigital web as a powerful propulsion generator. Therefore, we conclude that E. lutris is a complete aquatic animal, possessing differences in the proportions of the hindlimb muscles compared with those in other semi-aquatic and terrestrial mustelids. PMID:25715875

  15. Comparative functional anatomy of hindlimb muscles and bones with reference to aquatic adaptation of the sea otter.

    PubMed

    Mori, Kent; Suzuki, Satoshi; Koyabu, Daisuke; Kimura, Junpei; Han, Sung-Yong; Endo, Hideki

    2015-05-01

    Although the sea otter (Enhydra lutris) is a complete aquatic species, spending its entire life in the ocean, it has been considered morphologically to be a semi-aquatic animal. This study aimed to clarify the unique hindlimb morphology and functional adaptations of E. lutris in comparison to other Mustelidae species. We compared muscle mass and bone measurements of five Mustelidae species: the sea otter, Eurasian river otter (Lutra lutra), American mink (Neovison vison), Japanese weasel (Mustela itatsi) and Siberian weasel (M. sibirica). In comparison with the other 4 species, E. lutris possessed significantly larger gluteus, popliteus and peroneus muscles, but smaller adductor and ischiopubic muscles. The popliteus muscle may act as a medial rotator of the crus, and the peroneus muscle may act as an abductor of the fifth toe and/or the pronator of the foot. The bundles of the gluteus superficialis muscle of E. lutris were fused with those of the tensor fasciae latae muscle and gluteofemoralis muscles, and they may play a role in femur abduction. These results suggest that E. lutris uses the abducted femur, medially rotated crus, eversion of the ankle and abducted fifth digit or extended interdigital web as a powerful propulsion generator. Therefore, we conclude that E. lutris is a complete aquatic animal, possessing differences in the proportions of the hindlimb muscles compared with those in other semi-aquatic and terrestrial mustelids.

  16. Comparative functional anatomy of hindlimb muscles and bones with reference to aquatic adaptation of the sea otter.

    PubMed

    Mori, Kent; Suzuki, Satoshi; Koyabu, Daisuke; Kimura, Junpei; Han, Sung-Yong; Endo, Hideki

    2015-05-01

    Although the sea otter (Enhydra lutris) is a complete aquatic species, spending its entire life in the ocean, it has been considered morphologically to be a semi-aquatic animal. This study aimed to clarify the unique hindlimb morphology and functional adaptations of E. lutris in comparison to other Mustelidae species. We compared muscle mass and bone measurements of five Mustelidae species: the sea otter, Eurasian river otter (Lutra lutra), American mink (Neovison vison), Japanese weasel (Mustela itatsi) and Siberian weasel (M. sibirica). In comparison with the other 4 species, E. lutris possessed significantly larger gluteus, popliteus and peroneus muscles, but smaller adductor and ischiopubic muscles. The popliteus muscle may act as a medial rotator of the crus, and the peroneus muscle may act as an abductor of the fifth toe and/or the pronator of the foot. The bundles of the gluteus superficialis muscle of E. lutris were fused with those of the tensor fasciae latae muscle and gluteofemoralis muscles, and they may play a role in femur abduction. These results suggest that E. lutris uses the abducted femur, medially rotated crus, eversion of the ankle and abducted fifth digit or extended interdigital web as a powerful propulsion generator. Therefore, we conclude that E. lutris is a complete aquatic animal, possessing differences in the proportions of the hindlimb muscles compared with those in other semi-aquatic and terrestrial mustelids. PMID:25715875

  17. Acupuncture ameliorated skeletal muscle atrophy induced by hindlimb suspension in mice.

    PubMed

    Onda, Akiko; Jiao, Qibin; Nagano, Yasuharu; Akimoto, Takayuki; Miyamoto, Toshikazu; Minamisawa, Susumu; Fukubayashi, Toru

    2011-07-01

    Preventing skeletal muscle atrophy is critical for maintaining quality of life, but it is often a challenging goal for the elderly and patients with severe conditions. We hypothesized that acupuncture in place of exercise training is an alternative non-pharmacological intervention that can help to prevent muscle atrophy. To elucidate the effects of acupuncture on skeletal muscle atrophy caused by hindlimb suspension (HS), we performed acupuncture on mice according to two different methods: acupuncture with electrical stimulation (EA: electroacupuncture) and without electrical stimulation (MA: manual acupuncture). A needle was retained in the gastrocnemius muscle for 30 min every day for 2 weeks in the EA and MA groups. In the EA group, 30 min of repetitive electrical stimulation (1 Hz, 1 ms pulse width, 6.5 mA intensity) was also applied. HS significantly reduced muscle mass and the cross-sectional area of the soleus muscles. This HS-induced reduction was significantly improved in the EA group, although the level of improvement remained insufficient when compared with the control group. We found that the mRNA expression levels of atrogin-1 and MuRF1, which play a principal role in muscle-specific degradation as E3 ubiquitin ligases, were significantly increased in the HS group compared to the control group. EA and MA reduced the HS-induced upregulation of atrogin-1 (p<0.01 in EA and MA) and MuRF1 (p<0.01 in EA) mRNAs. We also found that the expression levels of PI3K, Akt1, TRPV4, adenosine A1 receptor, myostatin, and SIRT1 mRNAs tended to be increased by HS. EA and MA further increased the HS-induced upregulation of Akt1 (p<0.05 in MA) and TRPV4 (p<0.05 in MA) mRNAs. We concluded that acupuncture partially prevented skeletal muscle atrophy. This effect might be due to an increase in protein synthesis and a decrease in protein degradation.

  18. Tendon material properties vary and are interdependent among turkey hindlimb muscles

    PubMed Central

    Matson, Andrew; Konow, Nicolai; Miller, Samuel; Konow, Pernille P.; Roberts, Thomas J.

    2012-01-01

    SUMMARY The material properties of a tendon affect its ability to store and return elastic energy, resist damage, provide mechanical feedback and amplify or attenuate muscle power. While the structural properties of a tendon are known to respond to a variety of stimuli, the extent to which material properties vary among individual muscles remains unclear. We studied the tendons of six different muscles in the hindlimb of Eastern wild turkeys to determine whether there was variation in elastic modulus, ultimate tensile strength and resilience. A hydraulic testing machine was used to measure tendon force during quasi-static lengthening, and a stress–strain curve was constructed. There was substantial variation in tendon material properties among different muscles. Average elastic modulus differed significantly between some tendons, and values for the six different tendons varied nearly twofold, from 829±140 to 1479±106 MPa. Tendons were stretched to failure, and the stress at failure, or ultimate tensile stress, was taken as a lower-limit estimate of tendon strength. Breaking tests for four of the tendons revealed significant variation in ultimate tensile stress, ranging from 66.83±14.34 to 112.37±9.39 MPa. Resilience, or the fraction of energy returned in cyclic length changes was generally high, and one of the four tendons tested was significantly different in resilience from the other tendons (range: 90.65±0.83 to 94.02±0.71%). An analysis of correlation between material properties revealed a positive relationship between ultimate tensile strength and elastic modulus (r2=0.79). Specifically, stiffer tendons were stronger, and we suggest that this correlation results from a constrained value of breaking strain, which did not vary significantly among tendons. This finding suggests an interdependence of material properties that may have a structural basis and may explain some adaptive responses observed in studies of tendon plasticity. PMID:22771746

  19. Tendon material properties vary and are interdependent among turkey hindlimb muscles.

    PubMed

    Matson, Andrew; Konow, Nicolai; Miller, Samuel; Konow, Pernille P; Roberts, Thomas J

    2012-10-15

    The material properties of a tendon affect its ability to store and return elastic energy, resist damage, provide mechanical feedback and amplify or attenuate muscle power. While the structural properties of a tendon are known to respond to a variety of stimuli, the extent to which material properties vary among individual muscles remains unclear. We studied the tendons of six different muscles in the hindlimb of Eastern wild turkeys to determine whether there was variation in elastic modulus, ultimate tensile strength and resilience. A hydraulic testing machine was used to measure tendon force during quasi-static lengthening, and a stress-strain curve was constructed. There was substantial variation in tendon material properties among different muscles. Average elastic modulus differed significantly between some tendons, and values for the six different tendons varied nearly twofold, from 829±140 to 1479±106 MPa. Tendons were stretched to failure, and the stress at failure, or ultimate tensile stress, was taken as a lower-limit estimate of tendon strength. Breaking tests for four of the tendons revealed significant variation in ultimate tensile stress, ranging from 66.83±14.34 to 112.37±9.39 MPa. Resilience, or the fraction of energy returned in cyclic length changes was generally high, and one of the four tendons tested was significantly different in resilience from the other tendons (range: 90.65±0.83 to 94.02±0.71%). An analysis of correlation between material properties revealed a positive relationship between ultimate tensile strength and elastic modulus (r(2)=0.79). Specifically, stiffer tendons were stronger, and we suggest that this correlation results from a constrained value of breaking strain, which did not vary significantly among tendons. This finding suggests an interdependence of material properties that may have a structural basis and may explain some adaptive responses observed in studies of tendon plasticity. PMID:22771746

  20. Effects of epimuscular myofascial force transmission on sarcomere length of passive muscles in the rat hindlimb

    PubMed Central

    Tijs, Chris; van Dieën, Jaap H; Maas, Huub

    2015-01-01

    Results from imaging studies and finite element models suggest epimuscular myofascial effects on sarcomere lengths in series within muscle fibers. However, experimental evidence is lacking. We evaluated epimuscular myofascial effects on (1) muscle belly, fiber, and mean sarcomere length and (2) sarcomere length distribution within passive fibers of the rat tibialis anterior (TA) and soleus (SO) muscles. Hindlimbs (n = 24) were positioned in predefined knee (55°, 90°, 125°, 160°) and ankle (either 90° or 125°) angles, and fixed in a formaldehyde solution. Varying knee joint angle causes changes in muscle–tendon unit length of SO and TA’s synergists, but not of SO and TA. Whole fibers were taken from SO and TA and photographed along their length. Mean sarcomere length was assessed for the entire fiber and for the proximal, intermediate, and distal thirds (fiber segments) separately. Mean sarcomere length of the fiber was not affected by knee angle, neither for SO (mean: 2.44 ± 0.03 μm and 2.19 ± 0.05 μm for ankle angles of 90° and 125°, respectively) nor for TA (mean: 2.33 ± 0.05 μm and 2.51 ± 0.07 μm for ankle angle set to 90° and 125°, respectively). Only for TA, a significant interaction between knee angle and fiber segment was found, indicating changes in the distribution of lengths of in-series sarcomeres. Thus, while epimuscular myofascial force transmission did not cause mean sarcomere length changes within passive SO and TA, it did alter the length distribution of sarcomeres within passive TA. PMID:26537346

  1. Robot applied stance loading increases hindlimb muscle mass and stepping kinetics in a rat model of spinal cord injury.

    PubMed

    Nessler, Jeff A; Moustafa-Bayoumi, Moustafa; Soto, Dalziel; Duhon, Jessica E; Schmitt, Ryan

    2011-01-01

    Following spinal cord injury (SCI) reduced limb usage typically results in muscle atrophy. While robotic locomotor training has been shown to improve several aspects of stepping ability following SCI, little is known regarding the effects of automated training on the preservation of muscle function. The purpose of this study was to evaluate the effects of two robotic locomotor training algorithms on hindlimb strength and muscle mass in a rat model of SCI. Eighteen Sprague-Dawley rats received a mid-thoracic spinal cord transection at 5 days of age, and were randomly assigned to one of three groups: control (no training), standard robotic training, and robotic training with a downward force applied to the shank during the stance phase of gait. Training occurred 5 days/week for 5 min/day, and animals received 90% body weight support for all sessions. Following 4 weeks of training, vertical and propulsive ground reaction force during stepping and en vitro mass of two plantarflexor muscles were significantly increased for all of the trained animals when compared to the untrained control group. Post hoc analysis revealed that standard robotic training did not appear to increase ground reaction force and muscle mass to the same extent as the loaded condition. These results indicate that automated robotic training helps to preserve hindlimb muscle function in rats following SCI. Further, the addition of a plantarflexion stance load appears to promote greater increases in muscle mass and stepping kinetics.

  2. Electrophysiological Motor Unit Number Estimation (MUNE) Measuring Compound Muscle Action Potential (CMAP) in Mouse Hindlimb Muscles.

    PubMed

    Arnold, W David; Sheth, Kajri A; Wier, Christopher G; Kissel, John T; Burghes, Arthur H; Kolb, Stephen J

    2015-09-25

    Compound muscle action potential (CMAP) and motor unit number estimation (MUNE) are electrophysiological techniques that can be used to monitor the functional status of a motor unit pool in vivo. These measures can provide insight into the normal development and degeneration of the neuromuscular system. These measures have clear translational potential because they are routinely applied in diagnostic and clinical human studies. We present electrophysiological techniques similar to those employed in humans to allow recordings of mouse sciatic nerve function. The CMAP response represents the electrophysiological output from a muscle or group of muscles following supramaximal stimulation of a peripheral nerve. MUNE is an electrophysiological technique that is based on modifications of the CMAP response. MUNE is a calculated value that represents the estimated number of motor neurons or axons (motor control input) supplying the muscle or group of muscles being tested. We present methods for recording CMAP responses from the proximal leg muscles using surface recording electrodes following the stimulation of the sciatic nerve in mice. An incremental MUNE technique is described using submaximal stimuli to determine the average single motor unit potential (SMUP) size. MUNE is calculated by dividing the CMAP amplitude (peak-to-peak) by the SMUP amplitude (peak-to-peak). These electrophysiological techniques allow repeated measures in both neonatal and adult mice in such a manner that facilitates rapid analysis and data collection while reducing the number of animals required for experimental testing. Furthermore, these measures are similar to those recorded in human studies allowing more direct comparisons.

  3. Electrophysiological Motor Unit Number Estimation (MUNE) Measuring Compound Muscle Action Potential (CMAP) in Mouse Hindlimb Muscles.

    PubMed

    Arnold, W David; Sheth, Kajri A; Wier, Christopher G; Kissel, John T; Burghes, Arthur H; Kolb, Stephen J

    2015-01-01

    Compound muscle action potential (CMAP) and motor unit number estimation (MUNE) are electrophysiological techniques that can be used to monitor the functional status of a motor unit pool in vivo. These measures can provide insight into the normal development and degeneration of the neuromuscular system. These measures have clear translational potential because they are routinely applied in diagnostic and clinical human studies. We present electrophysiological techniques similar to those employed in humans to allow recordings of mouse sciatic nerve function. The CMAP response represents the electrophysiological output from a muscle or group of muscles following supramaximal stimulation of a peripheral nerve. MUNE is an electrophysiological technique that is based on modifications of the CMAP response. MUNE is a calculated value that represents the estimated number of motor neurons or axons (motor control input) supplying the muscle or group of muscles being tested. We present methods for recording CMAP responses from the proximal leg muscles using surface recording electrodes following the stimulation of the sciatic nerve in mice. An incremental MUNE technique is described using submaximal stimuli to determine the average single motor unit potential (SMUP) size. MUNE is calculated by dividing the CMAP amplitude (peak-to-peak) by the SMUP amplitude (peak-to-peak). These electrophysiological techniques allow repeated measures in both neonatal and adult mice in such a manner that facilitates rapid analysis and data collection while reducing the number of animals required for experimental testing. Furthermore, these measures are similar to those recorded in human studies allowing more direct comparisons. PMID:26436455

  4. Electrophysiological Motor Unit Number Estimation (MUNE) Measuring Compound Muscle Action Potential (CMAP) in Mouse Hindlimb Muscles

    PubMed Central

    Arnold, W. David; Sheth, Kajri A.; Wier, Christopher G.; Kissel, John T.; Burghes, Arthur H.; Kolb, Stephen J.

    2015-01-01

    Compound muscle action potential (CMAP) and motor unit number estimation (MUNE) are electrophysiological techniques that can be used to monitor the functional status of a motor unit pool in vivo. These measures can provide insight into the normal development and degeneration of the neuromuscular system. These measures have clear translational potential because they are routinely applied in diagnostic and clinical human studies. We present electrophysiological techniques similar to those employed in humans to allow recordings of mouse sciatic nerve function. The CMAP response represents the electrophysiological output from a muscle or group of muscles following supramaximal stimulation of a peripheral nerve. MUNE is an electrophysiological technique that is based on modifications of the CMAP response. MUNE is a calculated value that represents the estimated number of motor neurons or axons (motor control input) supplying the muscle or group of muscles being tested. We present methods for recording CMAP responses from the proximal leg muscles using surface recording electrodes following the stimulation of the sciatic nerve in mice. An incremental MUNE technique is described using submaximal stimuli to determine the average single motor unit potential (SMUP) size. MUNE is calculated by dividing the CMAP amplitude (peak-to-peak) by the SMUP amplitude (peak-to-peak). These electrophysiological techniques allow repeated measures in both neonatal and adult mice in such a manner that facilitates rapid analysis and data collection while reducing the number of animals required for experimental testing. Furthermore, these measures are similar to those recorded in human studies allowing more direct comparisons. PMID:26436455

  5. Skeletal muscle myostatin mRNA expression is fiber-type specific and increases during hindlimb unloading

    NASA Technical Reports Server (NTRS)

    Carlson, C. J.; Booth, F. W.; Gordon, S. E.

    1999-01-01

    Transgenic mice lacking a functional myostatin (MSTN) gene demonstrate greater skeletal muscle mass resulting from muscle fiber hypertrophy and hyperplasia (McPherron, A. C., A. M. Lawler, and S. -J. Lee. Nature 387: 83-90, 1997). Therefore, we hypothesized that, in normal mice, MSTN may act as a negative regulator of muscle mass. Specifically, we hypothesized that the predominately slow (type I) soleus muscle, which demonstrates greater atrophy than the fast (type II) gastrocnemius-plantaris complex (Gast/PLT), would show more elevation in MSTN mRNA abundance during hindlimb unloading (HU). Surprisingly, MSTN mRNA was not detectable in weight-bearing or HU soleus muscle, which atrophied 42% by the 7th day of HU in female ICR mice. In contrast, MSTN mRNA was present in weight-bearing Gast/PLT muscle and was significantly elevated (67%) at 1 day but not at 3 or 7 days of HU. However, the Gast/PLT muscle had only atrophied 17% by the 7th day of HU. Because the soleus is composed only of type I and IIa fibers, whereas the Gast/PLT expresses type IId/x and IIb in addition to type I and IIa, it was necessary to perform a more careful analysis of the relationship between MSTN mRNA levels and myosin heavy-chain (MHC) isoform expression (as a marker of fiber type). A significant correlation (r = 0.725, P < 0. 0005) was noted between the percentage of MHC isoform IIb expression and MSTN mRNA abundance in several muscles of the mouse hindlimb. These results indicate that MSTN expression is not strongly associated with muscle atrophy induced by HU; however, it is strongly associated with MHC isoform IIb expression in normal muscle.

  6. Hindlimb Muscle Morphology and Function in a New Atrophy Model Combining Spinal Cord Injury and Cast Immobilization

    PubMed Central

    Ye, Fan; Keener, Jonathon E.; Vohra, Ravneet; Lim, Wootaek; Ruhella, Arjun; Bose, Prodip; Daniels, Michael; Walter, Glenn, A.; Thompson, Floyd; Vandenborne, Krista

    2013-01-01

    Abstract Contusion spinal cord injury (SCI) animal models are used to study loss of muscle function and mass. However, parallels to the human condition typically have been confounded by spontaneous recovery observed within the first few post-injury weeks, partly because of free cage activity. We implemented a new rat model combining SCI with cast immobilization (IMM) to more closely reproduce the unloading conditions experienced by SCI patients. Magnetic resonance imaging was used to monitor hindlimb muscles' cross-sectional area (CSA) after SCI, IMM alone, SCI combined with IMM (SCI+IMM), and in controls (CTR) over a period of 21 days. Soleus muscle tetanic force was measured in situ on day 21, and hindlimb muscles were harvested for histology. IMM alone produced a decrease in triceps surae CSA to 63.9±4.9% of baseline values within 14 days. In SCI, CSA decreased to 75.0±10.5% after 7 days, and recovered to 77.9±10.7% by day 21. SCI+IMM showed the greatest amount of atrophy (56.9±9.9% on day 21). In all groups, muscle mass and soleus tetanic force decreased in parallel, such that specific force was maintained. Extensor digitorum longus (EDL) and soleus fiber size decreased in all groups, particularly in SCI+IMM. We observed a significant degree of asymmetry in muscle CSA in SCI but not IMM. This effect increased between day 7 and 21 in SCI, but also in SCI+IMM, suggesting a minor dependence on muscle activity. SCI+IMM offers a clinically relevant model of SCI to investigate the mechanistic basis for skeletal muscle adaptations after SCI and develop therapeutic approaches. PMID:22985272

  7. Dynamic Foot Pressure as a Countermeasure to Muscle Atrophy

    NASA Astrophysics Data System (ADS)

    Kyparos, A.; Layne, C. S.; Martinez, D. A.; Clarke, M. S. F.; Feeback, D. L.

    2002-01-01

    Mechanical unloading of skeletal muscle (SKM) as a consequence of space flight or ground-based analogues, such as human bedrest and rodent hindlimb suspension (HLS) models, induces SKM atrophy particularly affecting the anti-gravity musculature of the lower limbs. In the context of manned space flight, the subsequent loss of muscle strength and functionality will pose operational implications jeopardizing mission success. Exercise, currently the primary muscle degradation countermeasure, has not proven completely effective in preventing muscle atrophy. It is therefore imperative that some other forms of in- flight countermeasure be also developed to supplement the prescribed exercise regimen the astronauts follow during spaceflight. Previous work in both humans and rats has shown that mechanical stimulation of the soles of the feet increases neuromuscular activation in the lower limb musculature and that such stimulation results in the limited prevention of atrophy in the soleus muscle of unloaded rats. This study was designed to investigate the effect of cutaneous mechanoreceptor stimulation on hindlimb unloading- induced SKM atrophy in rats. It was hypothesized that mechanical stimulation of the plantar surface of the rat foot during hindlimb suspension (HLS), utilizing a novel stimulation paradigm known as Dynamic Foot Pressure (DFP), would attenuate unloading-induced SKM atrophy. Mature adult male Wistar rats were randomly assigned to four groups of 10 rats each as follows: sedentary controls (Ctrl), hindlimb suspended only (HLS), hindlimb suspended wearing an inflatable boot (HLS-IFL) and hindlimb suspended rats wearing a non-inflatable boot (HLS-NIFL). The stimulation of mechanoreceptors was achieved by applying pressure to the plantar surface of the foot during the 10-day period of HLS using a custom-built boot. The anti-atrophic effects of DFP application was quantified directly by morphological (muscle wet weight, myofiber cross-sectional area

  8. Growth hormone/IGF-I and/or resistive exercise maintains myonuclear number in hindlimb unweighted muscles

    NASA Technical Reports Server (NTRS)

    Allen, D. L.; Linderman, J. K.; Roy, R. R.; Grindeland, R. E.; Mukku, V.; Edgerton, V. R.

    1997-01-01

    In the present study of rats, we examined the role, during 2 wk of hindlimb suspension, of growth hormone/insulin-like growth factor I (GH/IGF-I) administration and/or brief bouts of resistance exercise in ameliorating the loss of myonuclei in fibers of the soleus muscle that express type I myosin heavy chain. Hindlimb suspension resulted in a significant decrease in mean soleus wet weight that was attenuated either by exercise alone or by exercise plus GH/IGF-I treatment but was not attenuated by hormonal treatment alone. Both mean myonuclear number and mean fiber cross-sectional area (CSA) of fibers expressing type I myosin heavy chain decreased after 2 wk of suspension compared with control (134 vs. 162 myonuclei/mm and 917 vs. 2,076 micron2, respectively). Neither GH/IGF-I treatment nor exercise alone affected myonuclear number or fiber CSA, but the combination of exercise and growth-factor treatment attenuated the decrease in both variables. A significant correlation was found between mean myonuclear number and mean CSA across all groups. Thus GH/IGF-I administration and brief bouts of muscle loading had an interactive effect in attenuating the loss of myonuclei induced by chronic unloading.

  9. Chronic Exercise Training Down-Regulates TNF-α and Atrogin-1/MAFbx in Mouse Gastrocnemius Muscle Atrophy Induced by Hindlimb Unloading.

    PubMed

    Al-Nassan, Saad; Fujita, Naoto; Kondo, Hiroyo; Murakami, Shinichiro; Fujino, Hidemi

    2012-12-26

    The purpose of this study was to investigate the effect of chronic moderate-intensity training in order to prevent muscle atrophy with a focus on TNF-α and atrogin-1/MAFbx as main proteolytic indicators. Hindlimb unloading model of mice received treadmill running exercise for 1 hr per day during hindlimb unloading period of 6 weeks. The gastrocnemius muscle mass, muscle fiber cross-sectional area, and succinate dehydrogenase (SDH) activity in the muscle fiber were higher in the exercised group, while TNF-α and atrogin-1/MAFbx mRNA expressions were significantly lower. Results in the present study showed that chronic exercise could prevent over expression of TNF-α and atrogin-1/MAFbx in the atrophied skeletal muscle, providing further support to the effects of chronic exercise training on muscle atrophy.

  10. Motoneuronal and muscle synergies involved in cat hindlimb control during fictive and real locomotion: a comparison study.

    PubMed

    Markin, Sergey N; Lemay, Michel A; Prilutsky, Boris I; Rybak, Ilya A

    2012-04-01

    We compared the activity profiles and synergies of spinal motoneurons recorded during fictive locomotion evoked in immobilized decerebrate cat preparations by midbrain stimulation to the activity profiles and synergies of the corresponding hindlimb muscles obtained during forward level walking in cats. The fictive locomotion data were collected in the Spinal Cord Research Centre, University of Manitoba, and provided by Dr. David McCrea; the real locomotion data were obtained in the laboratories of M. A. Lemay and B. I. Prilutsky. Scatterplot representation and minimum spanning tree clustering algorithm were used to identify the possible motoneuronal and muscle synergies operating during both fictive and real locomotion. We found a close similarity between the activity profiles and synergies of motoneurons innervating one-joint muscles during fictive locomotion and the profiles and synergies of the corresponding muscles during real locomotion. However, the activity patterns of proximal nerves controlling two-joint muscles, such as posterior biceps and semitendinosus (PBSt) and rectus femoris (RF), were not uniform in fictive locomotion preparations and differed from the activity profiles of the corresponding two-joint muscles recorded during forward level walking. Moreover, the activity profiles of these nerves and the corresponding muscles were unique and could not be included in the synergies identified in fictive and real locomotion. We suggest that afferent feedback is involved in the regulation of locomotion via motoneuronal synergies controlled by the spinal central pattern generator (CPG) but may also directly affect the activity of motoneuronal pools serving two-joint muscles (e.g., PBSt and RF). These findings provide important insights into the organization of the spinal CPG in mammals, the motoneuronal and muscle synergies engaged during locomotion, and their afferent control.

  11. Chronic hindlimb suspension unloading markedly decreases turnover rates of skeletal and cardiac muscle proteins and adipose tissue triglycerides.

    PubMed

    Bederman, Ilya R; Lai, Nicola; Shuster, Jeffrey; Henderson, Leigh; Ewart, Steven; Cabrera, Marco E

    2015-07-01

    We previously showed that a single bolus of "doubly-labeled" water ((2)H2 (18)O) can be used to simultaneously determine energy expenditure and turnover rates (synthesis and degradation) of tissue-specific lipids and proteins by modeling labeling patterns of protein-bound alanine and triglyceride-bound glycerol (Bederman IR, Dufner DA, Alexander JC, Previs SF. Am J Physiol Endocrinol Metab 290: E1048-E1056, 2006). Using this novel method, we quantified changes in the whole body and tissue-specific energy balance in a rat model of simulated "microgravity" induced by hindlimb suspension unloading (HSU). After chronic HSU (3 wk), rats exhibited marked atrophy of skeletal and cardiac muscles and significant decrease in adipose tissue mass. For example, soleus muscle mass progressively decreased 11, 43, and 52%. We found similar energy expenditure between control (90 ± 3 kcal · kg(-1)· day(-1)) and hindlimb suspended (81 ± 6 kcal/kg day) animals. By comparing food intake (∼ 112 kcal · kg(-1) · day(-1)) and expenditure, we found that animals maintained positive calorie balance proportional to their body weight. From multicompartmental fitting of (2)H-labeling patterns, we found significantly (P < 0.005) decreased rates of synthesis (percent decrease from control: cardiac, 25.5%; soleus, 70.3%; extensor digitorum longus, 44.9%; gastrocnemius, 52.5%; and adipose tissue, 39.5%) and rates of degradation (muscles: cardiac, 9.7%; soleus, 52.0%; extensor digitorum longus, 27.8%; gastrocnemius, 37.4%; and adipose tissue, 50.2%). Overall, HSU affected growth of young rats by decreasing the turnover rates of proteins in skeletal and cardiac muscles and adipose tissue triglycerides. Specifically, we found that synthesis rates of skeletal and cardiac muscle proteins were affected to a much greater degree compared with the decrease in degradation rates, resulting in large negative balance and significant tissue loss. In contrast, we found a small decrease in adipose tissue

  12. The adaptational strategies of the hindlimb muscles in the Tenrecidae species including the aquatic web-footed tenrec (Limnogale mergulus).

    PubMed

    Endo, Hideki; Yonezawa, Takahiro; Rakotondraparany, Felix; Sasaki, Motoki; Hasegawa, Masami

    2006-07-01

    The hindlimb muscles in four species of Tenrecidae (Oryzoryctinae: Talazac long-tailed tenrec and web-footed tenrec, Tenrecinae: lesser hedgehog tenrec, and streaked tenrec), were examined macroscopically. The weight ratios of the muscles to the body in the oryzoryctinid species are larger than those in Tenrecinae, since the Oryzoryctinae species have an obviously smaller body from the evolutionary point of view. It can be primarily pointed out that the adaptation of the body size is different between the two subfamilies, and secondarily, that functional adaptation to locomotion is complete within each subfamily. The weight data and the morphological findings demonstrate that the web-footed tenrec possesses an extraordinary large M. semimembranosus in comparison to the Talazac long-tailed tenrec in their weight ratios. This muscle may act as a strong flexor motor in the knee joint during the aquatic locomotion of the web-footed tenrec. Since the other muscles of the web-footed tenrec are similar to those of the Talazac long-tailed tenrec regards weight ratio data, we think that the web-footed tenrec may have derived from a terrestrial ancestor such as the long-tailed tenrecs. In Tenrecinae the streaked tenrec is equipped with larger Mm. adductores, M. semimembranosus and M. triceps surae than the lesser hedgehog tenrec. This species is adapted to fossorial life derived from non-specialized ancestors within the evolutionary lines of the spiny tenrecs.

  13. Muscle fibre type distribution of the thoracolumbar and hindlimb regions of horses: relating fibre type and functional role

    PubMed Central

    2014-01-01

    Background Although the majority of equine muscles have a mixed fibre type distribution indicative of diverse functional roles, the predominance of a fibre type can indicate the primary function of a muscle. The deep epaxial musculature has an important role in core spinal stability in humans, reflected as a predominantly muscle fibre type (MFT) I or postural fibre type. The fibre type of the deep epaxial musculature has not been determined in horses. The objective of the study was to determine the MFT distribution in selected muscles of thoracolumbar and hindlimb region of horses. This included deep epaxial and hypaxial muscles that were hypothesised to have a postural stabilising role. A second objective was to examine differences in MFT distribution between horses bred for endurance (Arabian) and sprinting (Quarter horse). Muscle biopsy samples were obtained from selected thoracolumbar and hind limb muscles of 5 Quarter horses, 4 Arabians, and 2 Thoroughbreds. The myosin heavy chain distribution was determined by gel electrophoresis. Mann–Whitney rank test was used to compare the proportional MFT and differences between breeds. Results Mm. sacrocaudalis dorsalis medialis and diaphragm had the highest proportion of MFT-I. The remaining deep epaxial muscles and the hypaxial muscle m. psoas minor had approximately equal MFT I and II proportions. Mm. psoas major, iliocostalis, longissimus dorsi and the hind limb muscles contained mostly MFT-IIX. The fibre type distribution was similar between Arabians and Quarter horses, although Quarter horses had more MFT-IIX fibres in psoas major (P = 0.02) while Arabians had more MFT-I fibres in m. longissimus dorsi (P = 0.03). Conclusions The fibre type distribution of the deep epaxial muscles, mm psoas minor and diaphragm varied from approximately equal MFT-I and II proportions to predominantly MFT-I suggesting a postural stabilising role possibly important in core spinal stability. In contrast the fibre type

  14. Differential adaptation to weightlessness of functional and structural characteristics of rat hindlimb muscles.

    PubMed

    Stevens, L; Picquet, F; Catinot, M P; Mounier, Y

    1996-09-01

    Soleus, vastus intermedius, tibialis anterior, and extensor digitorum longus muscles were removed from rats following space flight onboard the SLS-2 mission and from control animals. Muscle tissues were studied for their calcium and strontium activated tension characteristics and for structural changes. Muscles were also examined for myosin composition using electrophoresis. Results indicate that changes occurred in structural and functional muscle characteristics in both slow and fast muscle fiber types. These results are detailed and discussed.

  15. Passive stiffness of hindlimb muscles in anurans with distinct locomotor specializations.

    PubMed

    Danos, Nicole; Azizi, Emanuel

    2015-08-01

    Anurans (frogs and toads) have been shown to have relatively compliant skeletal muscles. Using a meta-analysis of published data we have found that muscle stiffness is negatively correlated with joint range of motion when examined across mammalian, anuran and bird species. Given this trend across a broad phylogenetic sample, we examined whether the relationship held true within anurans. We identified four species that differ in preferred locomotor mode and hence joint range of motion (Lithobates catesbeianus, Rhinella marina, Xenopus laevis and Kassina senegalensis) and hypothesized that smaller in vivo angles (more flexed) at the knee and ankle joint would be associated with more compliant extensor muscles. We measured passive muscle tension during cyclical stretching (20%) around L0 (sarcomere lengths of 2.2 μm) in fiber bundles extracted from cruralis and plantaris muscles. We found no relationship between muscle stiffness and range of motion for either muscle-joint complex. There were no differences in the passive properties of the cruralis muscle among the four species, but the plantaris muscles of the Xenopus and Kassina were significantly stiffer than those of the other two species. Our results suggest that in anurans the stiffness of muscle fibers is a relatively minor contributor to stiffness at the level of joints and that variation in other anatomical properties including muscle-tendon architecture and joint mechanics as well as active control likely contribute more significantly to range of motion during locomotion.

  16. Segmental distribution of the motor neuron columns that supply the rat hindlimb: A muscle/motor neuron tract-tracing analysis targeting the motor end plates.

    PubMed

    Mohan, R; Tosolini, A P; Morris, R

    2015-10-29

    Spinal cord injury (SCI) that disrupts input from higher brain centers to the lumbar region of the spinal cord results in paraplegia, one of the most debilitating conditions affecting locomotion. Non-human primates have long been considered to be the most appropriate animal to model lower limb dysfunction. More recently, however, there has been a wealth of scientific information gathered in the rat regarding the central control of locomotion. Moreover, rodent models of SCI at lumbar levels have been widely used to validate therapeutic scenarios aimed at the restoration of locomotor activities. Despite the growing use of the rat as a model of locomotor dysfunction, knowledge regarding the anatomical relationship between spinal cord motor neurons and the hindlimb muscles that they innervate is incomplete. Previous studies performed in our laboratory have shown the details of the muscle/motor neuron topographical relationship for the mouse forelimb and hindlimb as well as for the rat forelimb. The present analysis aims to characterize the segmental distribution of the motor neuron pools that innervate the muscles of the rat hindlimb, hence completing this series of studies. The location of the motor end plate (MEP) regions on the main muscles of the rat hindlimb was first revealed with acetylcholinesterase histochemistry. For each muscle under scrutiny, injections of Fluoro-Gold were then performed along the length of the MEP region. Targeting the MEPs gave rise to columns of motor neurons that span more spinal cord segments than previously reported. The importance of this study is discussed in terms of its application to gene therapy for SCI. PMID:26304758

  17. Proportion of fatigue-resistant motor units in hindlimb muscles of cat and their relation to axonal conduction velocity.

    PubMed Central

    Emonet-Dénand, F; Hunt, C C; Petit, J; Pollin, B

    1988-01-01

    1. A study of motor units to hindlimb muscles of cat has been made, with as complete a sample as possible of the motor axons to an individual muscle. In single experiments as much as 95% of the motor supply to a muscle has been examined. 2. The following muscles have been studied: peroneus brevis, peroneus tertius, peroneus longus, plantaris, gastrocnemius medialis, soleus, tenuissimus and lumbricalis superficialis. 3. Units were identified as slow resistant (S), fast resistant (FR), fast fatigable (FF) and fast intermediate (FI). The proportion of various motor unit types differs from one muscle to another. There is also some variation in the proportions to a given muscle from one animal to another. With the exceptions of soleus, which is entirely slow resistant, and gastrocnemius, which has relatively fewer resistant units, most muscles contain 60% or more of resistant (S and FR) units. 4. The conduction velocity ranges of FF, FR and FI units overlapped. There was little overlap between the conduction velocity ranges of these F units and of S units. 5. In individual experiments there was a strong and significant positive correlation between the logarithm of maximal tetanic tension and axonal conduction velocity in S and in S+FR units. In terms of contractile response the total fatigue-resistant population appeared to be a continuum. The correlation coefficient between maximal tetanic tension and conduction velocity was also high in the totality of units of all types, although within the FF group there appeared to be little or no correlation. In pooled data there was much more scatter and these relations were less clear. This resulted largely from differences in the ranges of axonal conduction velocity for a given motor unit type from one animal to another. 6. There was a highly significant negative correlation between isometric twitch contraction time and axonal conduction velocity in individual experiments. This relationship could also be seen, but less clearly

  18. Circadian force and EMG activity in hindlimb muscles of rhesus monkeys

    NASA Technical Reports Server (NTRS)

    Hodgson, J. A.; Wichayanuparp, S.; Recktenwald, M. R.; Roy, R. R.; McCall, G.; Day, M. K.; Washburn, D.; Fanton, J. W.; Kozlovskaya, I.; Edgerton, V. R.; Rumbaugh, D. M. (Principal Investigator)

    2001-01-01

    Continuous intramuscular electromyograms (EMGs) were recorded from the soleus (Sol), medial gastrocnemius (MG), tibialis anterior (TA), and vastus lateralis (VL) muscles of Rhesus during normal cage activity throughout 24-h periods and also during treadmill locomotion. Daily levels of MG tendon force and EMG activity were obtained from five monkeys with partial datasets from three other animals. Activity levels correlated with the light-dark cycle with peak activities in most muscles occurring between 08:00 and 10:00. The lowest levels of activity generally occurred between 22:00 and 02:00. Daily EMG integrals ranged from 19 mV/s in one TA muscle to 3339 mV/s in one Sol muscle: average values were 1245 (Sol), 90 (MG), 65 (TA), and 209 (VL) mV/s. The average Sol EMG amplitude per 24-h period was 14 microV, compared with 246 microV for a short burst of locomotion. Mean EMG amplitudes for the Sol, MG, TA, and VL during active periods were 102, 18, 20, and 33 microV, respectively. EMG amplitudes that approximated recruitment of all fibers within a muscle occurred for 5-40 s/day in all muscles. The duration of daily activation was greatest in the Sol [151 +/- 45 (SE) min] and shortest in the TA (61 +/- 19 min). The results show that even a "postural" muscle such as the Sol was active for only approximately 9% of the day, whereas less active muscles were active for approximately 4% of the day. MG tendon forces were generally very low, consistent with the MG EMG data but occasionally reached levels close to estimates of the maximum force generating potential of the muscle. The Sol and TA activities were mutually exclusive, except at very low levels, suggesting very little coactivation of these antagonistic muscles. In contrast, the MG activity usually accompanied Sol activity suggesting that the MG was rarely used in the absence of Sol activation. The results clearly demonstrate a wide range of activation levels among muscles of the same animal as well as among different

  19. Force-velocity and power characteristics of rat soleus muscle fibers after hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Mcdonald, K. S.; Blaser, C. A.; Fitts, R. H.

    1994-01-01

    The effects of 1, 2, and 3 wk of hindlimb suspension (HS) on force-velocity and power characteristics of single rat soleus fibers were determined. After 1, 2, or 3 wk of HA, small fiber bundles were isolated, placed in skinning solution, and stored at -20 C until studied. Single fibers were isolated and placed between a motor arm and force transducer, functional properties were studied, and fiber protein content was subsequently analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Additional fibers were isolated from soleus of control after 1 and 3 wk of HS, and fiber type distribution and myosin light chain stoichiometry were determined from SDS-PAGE analysis. After 1 wk of HS, percent type I fibers declined from 82 to 74%, whereas hybrid fibers increased from 10 to 18%. Percent fast type II fibers increased from 8% in control and 1 wk of HS to 26% by 3 wk of HS. Most fibers showed an increased unloaded maximal shortening velocity (V sub O)), but myosin heavy chain remained entirely slow type I. The mechanism for increased V(sub O) is unknown. There was a progressive decrease in fiber diameter and peak force after 1, 2, and 3 wk of HS, respectively. One week of HS resulted in a shift of the force-velocity curve, and between 2 and 3 wk of HS the curve shifted further such that V(sub O) was higher than control at all relative loads less than 45% peak isometric force. Peak absolute power output of soleus fibers progressively decreased through 2 wk of HS but showed no further change at 3 wk. The results suggest that between 2 and 3 wk the HS-induced alterations in the force-velocity relationship act to maintain the power output of single soleus fibers despite a continued reduction in fiber force.

  20. Force-Velocity and Power Characteristics of Rat Soleus Muscle Fibers after Hindlimb Suspension

    NASA Technical Reports Server (NTRS)

    McDonald, K. S.; Blaser, C. A.; Fitts, R. H.

    1994-01-01

    The effects of 1, 2, and 3 wk of Hindlimb Suspension (HS) on force-velocity and power characteristics of single rat soleus fibers were determined. After 1, 2, or 3 wk of HS, small fiber bundles were isolated, placed in skinning solution, and stored at -20 C until studied. Single fibers were isolated and placed between a motor arm and force transducer, functional properties were studied, and fiber protein content was subsequently analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Additional fibers were isolated from soleus of control and after 1 and 3 wk of HS, and fiber type distribution and myosin light chain stoichiometry were determined from SDS-PAGE analysis. After 1 wk of HS, percent type I fibers declined from 82 to 74%, whereas hybrid fibers increased from 10 to 18%. Percent fast type 11 fibers increased from 8% in control and 1 wk of HS to 26% by 3 wk of HS. Most fibers showed an increased unloaded maximal shortening velocity (V(sub 0)), but myosin heavy chain remained entirely slow type I. The mechanism for increased V(sub 0) is unknown. There was a progressive decrease in fiber diameter (14, 30, and 38%) and peak force (38, 56, and 63%) after 1, 2, and 3 wk of HS, respectively. One week of HS resulted in a shift of the force-velocity curve, and between 2 and 3 wk of HS the curve shifted further such that V(sub 0) was higher than control at all relative loads less than 45% peak isometric force. Peak absolute power output of soleus fibers progressively decreased through 2 wk of HS but showed no further change at 3 wk. The results suggest that between 2 and 3 wk the HS-induced alterations in the force-velocity relationship act to maintain the power output of single soleus fibers despite a continued reduction in fiber force.

  1. Investigations of the Effects of Altered Vestibular System Function on Hindlimb Anti-Gravity Muscles

    NASA Technical Reports Server (NTRS)

    Lowery, Mary Sue

    1998-01-01

    Exposure to different gravitational environments, both the microgravity of spaceflight and the hypergravity of centrifugation, result in altered vestibulo-spinal function which can be reversed by reacclimation to earth gravity (2). Control of orientation, posture, and locomotion are functions of the vestibular system which are altered by changes in gravitational environment. Not only is the vestibular system involved with coordination and proprioception, but the gravity sensing portion of the vestibular system also plays a major role in maintaining muscle tone through projections to spinal cord motoneurons that control anti-gravity muscles. I have been involved with investigations of several aspects of the link between vestibular inputs and muscle morphology and function during my work with Dr. Nancy Daunton this summer and the previous summer. We have prepared a manuscript for submission (4) to Aviation, Space, and Environmental Medicine based on work that I performed last summer in Dr. Daunton's lab. Techniques developed for that project will be utilized in subsequent experiments begun in the summer of 1998. I have been involved with the development of a pilot project to test the effects of vestibular galvanic stimulation (VGS) on anti-gravity muscles and in another project testing the effects of the ototoxic drug streptomycin on the otolith-spinal reflex and anti-gravity muscle morphology.

  2. Temporal Exposure of Cryptic Collagen Epitopes within Ischemic Muscle during Hindlimb Reperfusion

    PubMed Central

    Gagne, Paul J.; Tihonov, Nikita; Li, Xialou; Glaser, Joseph; Qiao, Jhenrong; Silberstein, Michael; Yee, Herman; Gagne, Elizabeth; Brooks, Peter

    2005-01-01

    Chronic limb-threatening ischemia is a devastating disease with limited surgical options. However, inducing controlled angiogenesis and enhancing reperfusion holds therapeutic promise. To gain a better understanding of the mechanisms that contribute to limb reperfusion, we examined the temporal biochemical and structural changes occurring within the extracellular matrix of ischemic skeletal muscle. Both the latent and active forms of MMP-2 and -9 significantly increased during the active phase of limb reperfusion. Moreover, small but significant alterations in tissue inhibitors of metalloproteinase levels also occurred during a similar time course, consistent with a net increase in extracellular matrix remodeling. This temporal increase in MMP activity coincided with enhanced exposure of the unique HU177 cryptic collagen epitope. Although the HUIV26 cryptic collagen epitope has been implicated in angiogenesis, little is known concerning such epitopes within ischemic muscle tissue. Here, we provide the first evidence that a functionally distinct cryptic collagen epitope (HU177) is temporally exposed in ischemic muscle tissue during the active phase of reperfusion. Interestingly, the exposure of the HU177 epitope was greatly diminished in MMP-9 null mice, corresponding with significantly reduced limb reperfusion. Therefore, the regulated exposure of a unique cryptic collagen epitope within ischemic muscle suggests an important role for collagen remodeling during the active phase of ischemic limb reperfusion. PMID:16251419

  3. [Hindlimb antigravity muscles' reaction in male and female rats to the deficit of functional loading].

    PubMed

    Il'ina-Kakueva, E I

    2002-01-01

    Histological and histomorphometric comparison of the antigravity muscles of rats of both sexes was performed following 30-d unloading of their hind limbs by head-down suspension. It was shown that growth rate of control males was higher as compared to control females. This is attributed to the synergic effects of somatotropin and testosterone on metabolism and growth of males and only somatotropin in females. Load deprivation of the hind limbs inhibited body mass gain in all animals; however, this inhibition was twice as great in males. Increase of the soleus and gastrocnemius in the control males in this experiment was slightly ahead of the muscle mass gain in the females. The histomorphometric investigation of the cross-section area of myofibers did not reveal differences between males and females either in the control or suspension. No difference was found in percent of various types of fibers in the control males and females. In the soleus of the suspended rats, a part of slow fibers had transformed into fast ones without any sex-related particularities. The conclusion was made that despite the significant difference in the hormonal profile, the reaction of males and females to insufficient weight loading of the antigravity muscles was alike.

  4. Hindlimb Skeletal Muscle Function and Skeletal Quality and Strength in +/G610C Mice With and Without Weight-Bearing Exercise.

    PubMed

    Jeong, Youngjae; Carleton, Stephanie M; Gentry, Bettina A; Yao, Xiaomei; Ferreira, J Andries; Salamango, Daniel J; Weis, MaryAnn; Oestreich, Arin K; Williams, Ashlee M; McCray, Marcus G; Eyre, David R; Brown, Marybeth; Wang, Yong; Phillips, Charlotte L

    2015-10-01

    Osteogenesis imperfecta (OI) is a heterogeneous heritable connective tissue disorder associated with reduced bone mineral density and skeletal fragility. Bone is inherently mechanosensitive, with bone strength being proportional to muscle mass and strength. Physically active healthy children accrue more bone than inactive children. Children with type I OI exhibit decreased exercise capacity and muscle strength compared with healthy peers. It is unknown whether this muscle weakness reflects decreased physical activity or a muscle pathology. In this study, we used heterozygous G610C OI model mice (+/G610C), which model both the genotype and phenotype of a large Amish OI kindred, to evaluate hindlimb muscle function and physical activity levels before evaluating the ability of +/G610C mice to undergo a treadmill exercise regimen. We found +/G610C mice hindlimb muscles do not exhibit compromised muscle function, and their activity levels were not reduced relative to wild-type mice. The +/G610C mice were also able to complete an 8-week treadmill regimen. Biomechanical integrity of control and exercised wild-type and +/G610C femora were analyzed by torsional loading to failure. The greatest skeletal gains in response to exercise were observed in stiffness and the shear modulus of elasticity with alterations in collagen content. Analysis of tibial cortical bone by Raman spectroscopy demonstrated similar crystallinity and mineral/matrix ratios regardless of sex, exercise, and genotype. Together, these findings demonstrate +/G610C OI mice have equivalent muscle function, activity levels, and ability to complete a weight-bearing exercise regimen as wild-type mice. The +/G610C mice exhibited increased femoral stiffness and decreased hydroxyproline with exercise, whereas other biomechanical parameters remain unaffected, suggesting a more rigorous exercise regimen or another exercise modality may be required to improve bone quality of OI mice.

  5. A Novel Intronic Single Nucleotide Polymorphism in the Myosin heavy polypeptide 4 Gene Is Responsible for the Mini-Muscle Phenotype Characterized by Major Reduction in Hind-Limb Muscle Mass in Mice

    PubMed Central

    Kelly, Scott A.; Bell, Timothy A.; Selitsky, Sara R.; Buus, Ryan J.; Hua, Kunjie; Weinstock, George M.; Garland, Theodore; Pardo-Manuel de Villena, Fernando; Pomp, Daniel

    2013-01-01

    Replicated artificial selection for high levels of voluntary wheel running in an outbred strain of mice favored an autosomal recessive allele whose primary phenotypic effect is a 50% reduction in hind-limb muscle mass. Within the High Runner (HR) lines of mice, the numerous pleiotropic effects (e.g., larger hearts, reduced total body mass and fat mass, longer hind-limb bones) of this hypothesized adaptive allele include functional characteristics that facilitate high levels of voluntary wheel running (e.g., doubling of mass-specific muscle aerobic capacity, increased fatigue resistance of isolated muscles, longer hind-limb bones). Previously, we created a backcross population suitable for mapping the responsible locus. We phenotypically characterized the population and mapped the Minimsc locus to a 2.6-Mb interval on MMU11, a region containing ∼100 known or predicted genes. Here, we present a novel strategy to identify the genetic variant causing the mini-muscle phenotype. Using high-density genotyping and whole-genome sequencing of key backcross individuals and HR mice with and without the mini-muscle mutation, from both recent and historical generations of the HR lines, we show that a SNP representing a C-to-T transition located in a 709-bp intron between exons 11 and 12 of the Myosin heavy polypeptide 4 (Myh4) skeletal muscle gene (position 67,244,850 on MMU11; assembly, December 2011, GRCm38/mm10; ENSMUSG00000057003) is responsible for the mini-muscle phenotype, Myh4Minimsc. Using next-generation sequencing, our approach can be extended to identify causative mutations arising in mouse inbred lines and thus offers a great avenue to overcome one of the most challenging steps in quantitative genetics. PMID:24056412

  6. Combined, but not individual, blockade of ASIC3, P2X, and EP4 receptors attenuates the exercise pressor reflex in rats with freely perfused hindlimb muscles.

    PubMed

    Stone, Audrey J; Copp, Steven W; Kim, Joyce S; Kaufman, Marc P

    2015-12-01

    In healthy humans, tests of the hypothesis that lactic acid, PGE2, or ATP plays a role in evoking the exercise pressor reflex proved controversial. The findings in humans resembled ours in decerebrate rats that individual blockade of the receptors to lactic acid, PGE2, and ATP had only small effects on the exercise pressor reflex provided that the muscles were freely perfused. This similarity between humans and rats prompted us to test the hypothesis that in rats with freely perfused muscles combined receptor blockade is required to attenuate the exercise pressor reflex. We first compared the reflex before and after injecting either PPADS (10 mg/kg), a P2X receptor antagonist, APETx2 (100 μg/kg), an activating acid-sensing ion channel 3 (ASIC) channel antagonist, or L161982 (2 μg/kg), an EP4 receptor antagonist, into the arterial supply of the hindlimb of decerebrated rats. We then examined the effects of combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the exercise pressor reflex using the same doses, intra-arterial route, and time course of antagonist injections as those used for individual blockade. We found that neither PPADS (n = 5), APETx2 (n = 6), nor L161982 (n = 6) attenuated the reflex. In contrast, combined blockade of these receptors (n = 7) attenuated the peak (↓27%, P < 0.019) and integrated (↓48%, P < 0.004) pressor components of the reflex. Combined blockade injected intravenously had no effect on the reflex. We conclude that combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the endings of thin fiber muscle afferents is required to attenuate the exercise pressor reflex in rats with freely perfused hindlimbs.

  7. Combined, but not individual, blockade of ASIC3, P2X, and EP4 receptors attenuates the exercise pressor reflex in rats with freely perfused hindlimb muscles.

    PubMed

    Stone, Audrey J; Copp, Steven W; Kim, Joyce S; Kaufman, Marc P

    2015-12-01

    In healthy humans, tests of the hypothesis that lactic acid, PGE2, or ATP plays a role in evoking the exercise pressor reflex proved controversial. The findings in humans resembled ours in decerebrate rats that individual blockade of the receptors to lactic acid, PGE2, and ATP had only small effects on the exercise pressor reflex provided that the muscles were freely perfused. This similarity between humans and rats prompted us to test the hypothesis that in rats with freely perfused muscles combined receptor blockade is required to attenuate the exercise pressor reflex. We first compared the reflex before and after injecting either PPADS (10 mg/kg), a P2X receptor antagonist, APETx2 (100 μg/kg), an activating acid-sensing ion channel 3 (ASIC) channel antagonist, or L161982 (2 μg/kg), an EP4 receptor antagonist, into the arterial supply of the hindlimb of decerebrated rats. We then examined the effects of combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the exercise pressor reflex using the same doses, intra-arterial route, and time course of antagonist injections as those used for individual blockade. We found that neither PPADS (n = 5), APETx2 (n = 6), nor L161982 (n = 6) attenuated the reflex. In contrast, combined blockade of these receptors (n = 7) attenuated the peak (↓27%, P < 0.019) and integrated (↓48%, P < 0.004) pressor components of the reflex. Combined blockade injected intravenously had no effect on the reflex. We conclude that combined blockade of P2X receptors, ASIC3 channels, and EP4 receptors on the endings of thin fiber muscle afferents is required to attenuate the exercise pressor reflex in rats with freely perfused hindlimbs. PMID:26472871

  8. Long-term perturbation of muscle iron homeostasis following hindlimb suspension in old rats is associated with high levels of oxidative stress and impaired recovery from atrophy

    PubMed Central

    Xu, Jinze; Hwang, Judy C.Y.; Lees, Hazel A.; Wohlgemuth, Stephanie E.; Knutson, Mitchell D.; Judge, Andrew R.; Dupont-Versteegden, Esther E.; Marzetti, Emanuele; Leeuwenburgh, Christiaan

    2015-01-01

    In the present study, we investigated the effects of 7 and 14 days of re-loading following 14-day muscle unweighting (hindlimb suspension, HS) on iron transport, non-heme iron levels and oxidative damage in the gastrocnemius muscle of young (6 months) and old (32 months) male Fischer 344×Brown Norway rats. Our results demonstrated that old rats had lower muscle mass, higher levels of total non-heme iron and oxidative damage in skeletal muscle in comparison with young rats. Non-heme iron concentrations and total non-heme iron amounts were 3.4- and 2.3-fold higher in aged rats as compared with their young counterparts, respectively. Seven and 14 days of re-loading was associated with higher muscle weights in young animals as compared with age-matched HS rats, but there was no difference in muscle weights among aged HS, 7 and 14 days of re-loading rats, indicating that aged rats may have a lower adaptability to muscle disuse and a lower capacity to recover from muscle atrophy. Protein levels of cellular iron transporters, such as divalent metal transport-1 (DMT1), transferrin receptor-1 (TfR1), Zip14, and ferroportin (FPN), and their mRNA abundance were determined. TfR1 protein and mRNA levels were significantly lower in aged muscle. Seven and 14 days of re-loading were associated with higher TfR1 mRNA and protein levels in young animals in comparison with their age-matched HS counterparts, but there was no difference between cohorts in aged animals, suggesting adaptive responses in the old to cope with iron deregulation. The extremely low expression of FPN in skeletal muscle might lead to inefficient iron export in the presence of iron overload and play a critical role in age-related iron accumulation in skeletal muscle. Moreover, oxidative stress was much greater in the muscles of the older animals measured as 4-hydroxy-2-nonhenal (HNE)-modified proteins and 8-oxo-7,8-dihydroguanosine levels. These markers remained fairly constant with either HS or re-loading in

  9. Effects of hindlimb unloading and ionizing radiation on skeletal muscle resistance artery vasodilation and its relation to cancellous bone in mice.

    PubMed

    Prisby, Rhonda D; Alwood, Joshua S; Behnke, Brad J; Stabley, John N; McCullough, Danielle J; Ghosh, Payal; Globus, Ruth K; Delp, Michael D

    2016-01-15

    Spaceflight has profound effects on vascular function as a result of weightlessness that may be further compounded by radiation exposure. The purpose of the present study was to assess the individual and combined effects of hindlimb unloading (HU) and radiation (Rad) on vasodilator responses in the skeletal muscle vasculature. Adult male C57BL/6J mice were randomized to one of four groups: control (Con), HU (tail suspension for 15 days), Rad (200 cGy of (137)Cs), and HU-Rad (15-day tail suspension and 200 cGy of (137)Cs). Endothelium-dependent vasodilation of gastrocnemius feed arteries was assessed in vitro using acetylcholine (ACh, 10(-9)-10(-4) M) and inhibitors of nitric oxide synthase (NOS) and cyclooxygenase (COX). Endothelium-independent vasodilation was assessed using Dea-NONOate (10(-9)-10(-4) M). Endothelium-dependent and -independent vasodilator responses were impaired relative to Con responses in all treatment groups; however, there was no further impairment from the combination of treatments (HU-Rad) relative to that in the HU and Rad groups. The NOS-mediated contribution to endothelium-dependent vasodilation was depressed with HU and Rad. This impairment in NOS signaling may have been partially compensated for by an enhancement of PGI2-mediated dilation. Changes in endothelium-dependent vasodilation were also associated with decrements in trabecular bone volume in the proximal tibia metaphysis. These data demonstrate that the simulated space environment (i.e., radiation exposure and unloading of muscle and bone) significantly impairs skeletal muscle artery vasodilation, mediated through endothelium-dependent reductions in NOS signaling and decrements in vascular smooth muscle cell responsiveness to NO.

  10. The protective effects of Chinese herb-Taikong Yangxin Prescription on the atrophic remodeling of cardiac muscle in rats induced by hindlimb unloading through activating Akt/GSK-3beta signaling pathway

    NASA Astrophysics Data System (ADS)

    Ming, Yuan; Min, Yuan; Jianfeng, Zhang; Zhili, Li; Huijuan, Wang; Desheng, Wang; Yinghui, Li; Yongzhi, Li; Shizhong, Jiang

    Objective To test the hypothesis that traditional Chinese herb-TaiKong Yangxin Prescrip-tion can activate the Akt/GSK-3β signaling pathway and alleviate the atrophic remodeling of cardiac muscle in rats induced by hindlimb unloading. Methods The physiological effects of simulated microgravity was induced by 7d hindlimb unloading in rats. TaiKong Yangxin Pre-scription was given daily by gastric irrigation as countermeasure against effects of simulated microgravity. The frozen sections of left ventricular cardiac muscles were stained by FITC la-beled lectin and visualized by laser scanning confocal microscopy, the cross section areas(CSA) of cardiomyocytes were calculated by IPP6.0 Image software. The protein expression of TnI, phosphorylation level of Akt and GSK-3β were measured by Western blot. Results Simulated microgravity decreased the CSA of cardiomyocytes and protein expression of TnI in left ven-tricular cardiac muscles, inhibited the phosphorylation level of Akt at serine 473 and GSK-3β at serine 9. The traditional Chinese herb-TaiKong Yangxin Prescription alleviated the atrophic remodeling of cardiac muscles, reversed the declined protein expression of TnI and phosphoryla-tion levels of Akt at serine 473 and GSK-3β at serine 9 in hindlimb-unloading rats. Conclusion The traditional Chinese herb-TaiKong Yangxin Prescription has significant countermeasure effects on the atrophic remodeling of cardiac muscle induced by hindlimb unloading in rats, in which activating Akt/GSK-3β signaling pathway plays an important role.(Funded by Advanced space medico-engineering research project of China, grant NO. 2005SY5206005 and SJ200801)

  11. High-field (11.75T) multimodal MR imaging of exercising hindlimb mouse muscles using a non-invasive combined stimulation and force measurement device.

    PubMed

    Gondin, Julien; Vilmen, Christophe; Cozzone, Patrick J; Bendahan, David; Duhamel, Guillaume

    2014-08-01

    We have designed and constructed an experimental set-up allowing electrical stimulation of hindlimb mouse muscles and the corresponding force measurements at high-field (11.75T). We performed high-resolution multimodal MRI (including T2 -weighted imaging, angiography and diffusion) and analysed the corresponding MRI changes in response to a stimulation protocol. Mice were tested twice over a 1-week period to investigate the reliability of mechanical measurements and T2 changes associated with the stimulation protocol. Additionally, angiographic images were obtained before and immediately after the stimulation protocol. Finally, multislice diffusion imaging was performed before, during and immediately after the stimulation session. Apparent diffusion coefficient (ADC) maps were calculated on the basis of diffusion weighted images (DWI). Both force production and T2 values were highly reproducible as illustrated by the low coefficient of variation (<8%) and high intraclass correlation coefficient (≥0.75) values. Maximum intensity projection angiographic images clearly showed a strong vascular effect resulting from the stimulation protocol. Although a motion sensitive imaging sequence was used (echo planar imaging) and in spite of the strong muscle contractions, motion artifacts were minimal for DWI recorded under exercising conditions, thereby underlining the robustness of the measurements. Mean ADC values increased under exercising conditions and were higher during the recovery period as compared with the corresponding control values. The proposed experimental approach demonstrates accurate high-field multimodal MRI muscle investigations at a preclinical level which is of interest for monitoring the severity and/or the progression of neuromuscular diseases but also for assessing the efficacy of potential therapeutic interventions.

  12. Effects of High-LET Radiation Exposure and Hindlimb Unloading on Skeletal Muscle Resistance Artery Vasomotor Properties and Cancellous Bone Microarchitecture in Mice.

    PubMed

    Ghosh, Payal; Behnke, Brad J; Stabley, John N; Kilar, Cody R; Park, Yoonjung; Narayanan, Anand; Alwood, Joshua S; Shirazi-Fard, Yasaman; Schreurs, Ann-Sofie; Globus, Ruth K; Delp, Michael D

    2016-03-01

    Weightlessness during spaceflight leads to functional changes in resistance arteries and loss of cancellous bone, which may be potentiated by radiation exposure. The purpose of this study was to assess the effects of hindlimb unloading (HU) and total-body irradiation (TBI) on the vasomotor responses of skeletal muscle arteries. Male C57BL/6 mice were assigned to control, HU (13-16 days), TBI (1 Gy (56)Fe, 600 MeV, 10 cGy/min) and HU-TBI groups. Gastrocnemius muscle feed arteries were isolated for in vitro study. Endothelium-dependent (acetylcholine) and -independent (Dea-NONOate) vasodilator and vasoconstrictor (KCl, phenylephrine and myogenic) responses were evaluated. Arterial endothelial nitric oxide synthase (eNOS), superoxide dismutase-1 (SOD-1) and xanthine oxidase (XO) protein content and tibial cancellous bone microarchitecture were quantified. Endothelium-dependent and -independent vasodilator responses were impaired in all groups relative to control, and acetylcholine-induced vasodilation was lower in the HU-TBI group relative to that in the HU and TBI groups. Reductions in endothelium-dependent vasodilation correlated with a lower cancellous bone volume fraction. Nitric oxide synthase inhibition abolished all group differences in endothelium-dependent vasodilation. HU and HU-TBI resulted in decreases in eNOS protein levels, while TBI and HU-TBI produced lower SOD-1 and higher XO protein content. Vasoconstrictor responses were not altered. Reductions in NO bioavailability (eNOS), lower anti-oxidant capacity (SOD-1) and higher pro-oxidant capacity (XO) may contribute to the deficits in NOS signaling in skeletal muscle resistance arteries. These findings suggest that the combination of insults experienced in spaceflight leads to impairment of vasodilator function in resistance arteries that is mediated through deficits in NOS signaling. PMID:26930379

  13. Responses of amino acids in hindlimb muscles to recovery from hypogravity and unloading by tail-cast suspension

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.; Henriksen, E. J.; Jacob, S.; Cook, P. H.

    1985-01-01

    Amino acids were assayed in muscles from rats exposed to 7 days of hypogravity and 12 h of gravity (F) or 6 days of suspension with (R) or without (H) 12 h of loading. In these groups, lower aspartate was common only to the soleus (SOL) relative to control muscles, the smallest difference being in group R. This difference in aspartate for F and H, but not for R, correlated with lower malate suggesting diminution of citric acid cycle intermediates. The R SOL value was increased over the H SOL. Therefore desite 12 h of loading, the F SOL was more comparable to the H SOL. The role of stress in preventing recovery of the F SOL was apparent from the ratios of glutamine/glutamate. Synthesis of glutamine is enhanced by glucocorticoids and is reflected by an increased ratio. In 5 of the 6 F muscles studied, this ratio was greater than in controls. In contrast, the ratio in all R muscles was similar to controls and showed recovery from the values in H muscles. Hence the post-flight treatment of F rats may have produced additional stress. Despite this stress, in some respects the SOL responses to hypogravity were similar to its responses to unloding by suspension.

  14. Fiber size, type, and myosin heavy chain content in rhesus hindlimb muscles after 2 weeks at 2 G

    NASA Technical Reports Server (NTRS)

    Tavakol, Morteza; Roy, Roland R.; Kim, Jung A.; Zhong, Hui; Hodgson, John A.; Hoban-Higgins, Tana M.; Fuller, Charles A.; Edgerton, V. Reggie

    2002-01-01

    BACKGROUND: Fiber atrophy and an increase in the percentage of fast fibers have been observed in Rhesus leg muscles after spaceflight. Hypothesis: Hypergravity will result in muscle fiber hypertrophy and an increase in the percentage of slow fibers. METHODS: Open muscle biopsies were obtained from Rhesus soleus, medial gastrocnemius (MG), and tibialis anterior (TA) muscles before and after 14 d of centrifugation (2 G) and in time-matched controls. Cage activity levels were measured by telemetry. RESULTS: Based on monoclonal antibody binding for myosin heavy chains (MHC), the fastest region of soleus contained a higher proportion of type I+II (27 vs. 13%) and had a tendency for a lower proportion of type I (38 vs. 61%, p = 0.10) fibers after than before centrifugation. There was a higher proportion of type I+II fibers in post- vs. pre-2 G (10 vs. 0.6%) MG biopsies. Fiber type distribution and MHC composition were unaffected in the TA. Overall, mean fiber sizes were unaffected by centrifugation. Average cage activity levels were 36% lower during than before 2 G. CONCLUSIONS: Our hypothesis was rejected. The changes in the proportion of fibers expressing type I MHC are the reverse of that expected with chronic loading of extensors and, paradoxically, are similar to changes observed with chronic unloading, such as occurs during spaceflight, in this primate model. The data are consistent with the observed decrease in total daily activity levels.

  15. Effects of alprostadil and iloprost on renal, lung, and skeletal muscle injury following hindlimb ischemia–reperfusion injury in rats

    PubMed Central

    Erer, Dilek; Özer, Abdullah; Demirtaş, Hüseyin; Gönül, İpek Işık; Kara, Halil; Arpacı, Hande; Çomu, Faruk Metin; Oktar, Gürsel Levent; Arslan, Mustafa; Küçük, Ayşegül

    2016-01-01

    Objectives To evaluate the effects of alprostadil (prostaglandin [PGE1] analog) and iloprost (prostacyclin [PGI2] analog) on renal, lung, and skeletal muscle tissues after ischemia reperfusion (I/R) injury in an experimental rat model. Materials and methods Wistar albino rats underwent 2 hours of ischemia via infrarenal aorta clamping with subsequent 2 hours of reperfusion. Alprostadil and iloprost were given starting simultaneously with the reperfusion period. Effects of agents on renal, lung, and skeletal muscle (gastrocnemius) tissue specimens were examined. Results Renal medullary congestion, cytoplasmic swelling, and mean tubular dilatation scores were significantly lower in the alprostadil-treated group than those found in the I/R-only group (P<0.0001, P=0.015, and P<0.01, respectively). Polymorphonuclear leukocyte infiltration, pulmonary partial destruction, consolidation, alveolar edema, and hemorrhage scores were significantly lower in alprostadil- and iloprost-treated groups (P=0.017 and P=0.001; P<0.01 and P<0.0001). Polymorphonuclear leukocyte infiltration scores in skeletal muscle tissue were significantly lower in the iloprost-treated group than the scores found in the nontreated I/R group (P<0.0001). Conclusion Alprostadil and iloprost significantly reduce lung tissue I/R injury. Alprostadil has more prominent protective effects against renal I/R injury, while iloprost is superior in terms of protecting the skeletal muscle tissue against I/R injury.

  16. Effects of alprostadil and iloprost on renal, lung, and skeletal muscle injury following hindlimb ischemia–reperfusion injury in rats

    PubMed Central

    Erer, Dilek; Özer, Abdullah; Demirtaş, Hüseyin; Gönül, İpek Işık; Kara, Halil; Arpacı, Hande; Çomu, Faruk Metin; Oktar, Gürsel Levent; Arslan, Mustafa; Küçük, Ayşegül

    2016-01-01

    Objectives To evaluate the effects of alprostadil (prostaglandin [PGE1] analog) and iloprost (prostacyclin [PGI2] analog) on renal, lung, and skeletal muscle tissues after ischemia reperfusion (I/R) injury in an experimental rat model. Materials and methods Wistar albino rats underwent 2 hours of ischemia via infrarenal aorta clamping with subsequent 2 hours of reperfusion. Alprostadil and iloprost were given starting simultaneously with the reperfusion period. Effects of agents on renal, lung, and skeletal muscle (gastrocnemius) tissue specimens were examined. Results Renal medullary congestion, cytoplasmic swelling, and mean tubular dilatation scores were significantly lower in the alprostadil-treated group than those found in the I/R-only group (P<0.0001, P=0.015, and P<0.01, respectively). Polymorphonuclear leukocyte infiltration, pulmonary partial destruction, consolidation, alveolar edema, and hemorrhage scores were significantly lower in alprostadil- and iloprost-treated groups (P=0.017 and P=0.001; P<0.01 and P<0.0001). Polymorphonuclear leukocyte infiltration scores in skeletal muscle tissue were significantly lower in the iloprost-treated group than the scores found in the nontreated I/R group (P<0.0001). Conclusion Alprostadil and iloprost significantly reduce lung tissue I/R injury. Alprostadil has more prominent protective effects against renal I/R injury, while iloprost is superior in terms of protecting the skeletal muscle tissue against I/R injury. PMID:27601882

  17. Muscle fatigue resistance in the rat hindlimb in vivo from low dietary intakes of tuna fish oil that selectively increase phospholipid n-3 docosahexaenoic acid according to muscle fibre type.

    PubMed

    Henry, R; Peoples, G E; McLennan, P L

    2015-09-28

    Dietary fish oil (FO) modulates muscle O2 consumption and contractile function, predictive of effects on muscle fatigue. High doses unattainable through human diet and muscle stimulation parameters used engender uncertainty in their physiological relevance. We tested the hypothesis that nutritionally relevant FO doses can modulate membrane fatty acid composition and muscle fatigue. Male Sprague-Dawley rats were randomised to control (10% olive oil (OO) by weight) or low or moderate FO diet (LowFO and ModFO) (HiDHA tuna fish oil) for 15 weeks (LowFO: 0.3% FO, 9.7% OO, 0.25% energy as EPA+DHA; ModFO: 1.25% FO, 8.75% OO, 1.0% energy as EPA+DHA). Hindlimb muscle function was assessed under anaesthesia in vivo using repetitive 5 s burst sciatic nerve stimulation (0.05 ms, 7-12 V, 5 Hz, 10 s duty cycle, 300 s). There were no dietary differences in maximum developed muscle force. Repetitive peak developed force fell to 50% within 62 (SEM 10) s in controls and took longer to decline in FO-fed rats (LowFO 110 (SEM 15) s; ModFO 117 (sem 14) s) (P<0.05). Force within bursts was better sustained with FO and maximum rates of force development and relaxation declined more slowly. The FO-fed rats incorporated higher muscle phospholipid DHA-relative percentages than controls (P<0.001). Incorporation of DHA was greater in the fast-twitch gastrocnemius (Control 9.3 (SEM 0.8) %, LowFO 19.9 (SEM 0.4), ModFO 24.3 (SEM 1.0)) than in the slow-twitch soleus muscle (Control 5.1 (SEM 0.2), LowFO 14.3 (SEM 0.7), ModFO 18.0 (SEM 1.4)) (P<0.001), which was comparable with the myocardium, in line with muscle fibre characteristics. The LowFO and ModFO diets, emulating human dietary and therapeutic supplement intake, respectively, both elicited muscle membrane DHA enrichment and fatigue resistance, providing a foundation for translating these physiological effects to humans. PMID:26266774

  18. Muscle fatigue resistance in the rat hindlimb in vivo from low dietary intakes of tuna fish oil that selectively increase phospholipid n-3 docosahexaenoic acid according to muscle fibre type.

    PubMed

    Henry, R; Peoples, G E; McLennan, P L

    2015-09-28

    Dietary fish oil (FO) modulates muscle O2 consumption and contractile function, predictive of effects on muscle fatigue. High doses unattainable through human diet and muscle stimulation parameters used engender uncertainty in their physiological relevance. We tested the hypothesis that nutritionally relevant FO doses can modulate membrane fatty acid composition and muscle fatigue. Male Sprague-Dawley rats were randomised to control (10% olive oil (OO) by weight) or low or moderate FO diet (LowFO and ModFO) (HiDHA tuna fish oil) for 15 weeks (LowFO: 0.3% FO, 9.7% OO, 0.25% energy as EPA+DHA; ModFO: 1.25% FO, 8.75% OO, 1.0% energy as EPA+DHA). Hindlimb muscle function was assessed under anaesthesia in vivo using repetitive 5 s burst sciatic nerve stimulation (0.05 ms, 7-12 V, 5 Hz, 10 s duty cycle, 300 s). There were no dietary differences in maximum developed muscle force. Repetitive peak developed force fell to 50% within 62 (SEM 10) s in controls and took longer to decline in FO-fed rats (LowFO 110 (SEM 15) s; ModFO 117 (sem 14) s) (P<0.05). Force within bursts was better sustained with FO and maximum rates of force development and relaxation declined more slowly. The FO-fed rats incorporated higher muscle phospholipid DHA-relative percentages than controls (P<0.001). Incorporation of DHA was greater in the fast-twitch gastrocnemius (Control 9.3 (SEM 0.8) %, LowFO 19.9 (SEM 0.4), ModFO 24.3 (SEM 1.0)) than in the slow-twitch soleus muscle (Control 5.1 (SEM 0.2), LowFO 14.3 (SEM 0.7), ModFO 18.0 (SEM 1.4)) (P<0.001), which was comparable with the myocardium, in line with muscle fibre characteristics. The LowFO and ModFO diets, emulating human dietary and therapeutic supplement intake, respectively, both elicited muscle membrane DHA enrichment and fatigue resistance, providing a foundation for translating these physiological effects to humans.

  19. Force, velocity and energy dynamics of nine load-moving muscles.

    PubMed

    Baratta, R V; Solomonow, M; Best, R; D'Ambrosia, R

    1997-01-01

    Nine architecturally different muscles of the cat's hindlimb were investigated with respect to the kinetic energy, the potential energy, and the force variations associated with shortening contractions against gravitational loads. Insight about the energy dynamics of contractile muscle can provide a unifying concept for models of muscle performance capability. In this study, it was found that as contractions shortened from passive equilibrium against a constant mass load, acceleration and deceleration phases appeared. These phase were associated with muscular force variations of up to 25% of the mass weight in fast twitch muscles at low loads. In contrast, slow twitch muscles were associated with less than 10% force variations when shortening against a gravitational load. It also was found that optimal loads exist which maximize each muscle's ability to impart kinetic and potential energy, these optimal loads tend to be in the mid-force range for highly pennate muscle and in the low-force range for justform muscles. It was concluded that the kinetic energy provided by each muscle is a small percentage of that calculated from its length-force relationship, especially at low loads. This study confirms that the efficiency of kinetic energy conversion is very low at low loads (gradually improving as the loads increase) and thereby substantiates early experiments with heat and metabolic energy.

  20. Hindlimb unloading alters ligament healing

    NASA Technical Reports Server (NTRS)

    Provenzano, Paolo P.; Martinez, Daniel A.; Grindeland, Richard E.; Dwyer, Kelley W.; Turner, Joanne; Vailas, Arthur C.; Vanderby, Ray Jr

    2003-01-01

    We investigated the hypothesis that hindlimb unloading inhibits healing in fibrous connective tissue such as ligament. Male rats were assigned to 3- and 7-wk treatment groups with three subgroups each: sham control, ambulatory healing, and hindlimb-suspended healing. Ambulatory and suspended animals underwent surgical rupture of their medial collateral ligaments, whereas sham surgeries were performed on control animals. After 3 or 7 wk, mechanical and/or morphological properties were measured in ligament, muscle, and bone. During mechanical testing, most suspended ligaments failed in the scar region, indicating the greatest impairment was to ligament and not to bone-ligament insertion. Ligament testing revealed significant reductions in maximum force, ultimate stress, elastic modulus, and low-load properties in suspended animals. In addition, femoral mineral density, femoral strength, gastrocnemius mass, and tibialis anterior mass were significantly reduced. Microscopy revealed abnormal scar formation and cell distribution in suspended ligaments with extracellular matrix discontinuities and voids between misaligned, but well-formed, collagen fiber bundles. Hence, stress levels from ambulation appear unnecessary for formation of fiber bundles yet required for collagen to form structurally competent continuous fibers. Results support our hypothesis that hindlimb unloading impairs healing of fibrous connective tissue. In addition, this study provides compelling morphological evidence explaining the altered structure-function relationship in load-deprived healing connective tissue.

  1. ‘Fast’ and ‘slow’ muscle fibres in hindlimb muscles of adult rats regenerate from intrinsically different satellite cells

    PubMed Central

    Kalhovde, JM; Jerkovic, R; Sefland, I; Cordonnier, C; Calabria, E; Schiaffino, S; Lømo, T

    2005-01-01

    Myosin heavy chain (MyHC) expression was examined in regenerating fast extensor digitorum longus (EDL) and slow soleus (SOL) muscles of adult rats. Myotoxic bupivacaine was injected into SOL and EDL and the muscles were either denervated or neuromuscularly blocked by tetrodotoxin (TTX) on the sciatic nerve. Three to 10 or 30 days later, denervated SOL or EDL, or innervated but neuromuscularly blocked EDL received a slow 20 Hz stimulus pattern through electrodes implanted on the muscles or along the fibular nerve to EDL below the TTX block. In addition, denervated SOL and EDL received a fast 100 Hz stimulus pattern. Denervated EDL and SOL stimulated with the same slow stimulus pattern expressed different amounts of type 1 MyHC protein (8%versus 35% at 10 days, 13%versus 87% at 30 days). Stimulated denervated and stimulated innervated (TTX blocked) EDL expressed the same amounts of type 1, 2A, 2X and 2B MyHC proteins. Cross-sections treated for in situ hybridization and immunocytochemistry showed expression of type 1 MyHC in all SOL fibres but only in some scattered single or smaller groups of fibres in EDL. The results suggest that muscle fibres regenerate from intrinsically different satellite cells in EDL and SOL and within EDL. However, induction by different extrinsic factors arising in extracellular matrix or from muscle position and usage in the limb has not been excluded. No evidence for nerve-derived trophic influences was obtained. PMID:15564285

  2. Unilateral hindlimb casting induced a delayed generalized muscle atrophy during rehabilitation that is prevented by a whey or a high protein diet but not a free leucine-enriched diet.

    PubMed

    Magne, Hugues; Savary-Auzeloux, Isabelle; Migné, Carole; Peyron, Marie-Agnès; Combaret, Lydie; Rémond, Didier; Dardevet, Dominique

    2013-01-01

    Sarcopenia is the general muscle mass and strength loss associated with ageing. Muscle atrophy could be made worse by exposure to acute periods of immobilization, because muscle disuse by itself is a stimulus for atrophy. Using a model of unilateral hindlimb casting in old adult rats, we have already demonstrated that the primary effect of immobilization was atrophy in the casted leg, but was also surprisingly associated with a retarded atrophy in the non-casted leg during rehabilitation. In search of mechanisms involved in this generalized atrophy, we demonstrated in the present study that contrary to pair-fed non-immobilized control animals, muscle protein synthesis in the non-immobilized limb was unable to adapt and to respond positively to food intake. Because pair-fed control rats did not lose muscle mass, this defect in muscle protein synthesis may represent one of the explanation for the muscle mass loss observed in the non-immobilized rats. Nevertheless, in order to stimulate protein turn over and generate a positive nitrogen balance required to maintain the whole muscle mass in immobilized rats, we tested a dietary free leucine supplementation (an amino acid known for its stimulatory effect on protein metabolism) during the rehabilitation period. Leucine supplementation was able to overcome the anabolic resistance in the non-immobilized limb. A greater muscle protein synthesis up-regulation associated with a stimulation of the mTOR signalling pathway was indeed recorded but it remained inefficient to prevent the loss of muscle in the non-immobilized limb. By contrast, we demonstrated here that whey protein or high protein diets were able to prevent the muscle mass loss of the non-immobilized limb by sustaining muscle protein synthesis during the entire rehabilitation period.

  3. Effects of Hindlimb Unweighting on Arterial Contractile Responses in Mice

    NASA Technical Reports Server (NTRS)

    Ma, Jia; Ren, Xin-Ling; Purdy, Ralph E.

    2003-01-01

    The aim of this work was to determine if hindlimb unweighting in mice alters arterial contractile responses. Sixteen male C57B/6 mice and 16 male Chinese Kunming mice were divided into control and 3 weeks hindlimb unweighting groups, respectively. Using isolated arterial rings from different arteries of mouse, effects of 3 weeks hindlimb unweighting on arterial contractile responsiveness were examined in vitro. The results showed that, in arterial rings from both C57B/6 and Chinese Kunming mice, maximum isometric contractile tensions evoked by either KCl or phenylephrine were significantly lower in abdominal aortic, mesenteric arterial and femoral arterial rings from hindlimb unweighting, compared to control mice. However, the maximal contractile responses of common carotid rings to KCl and PE were not significantly different between control and hindlimb unweighting groups. The sensitivity (EC(sub 50)) of all arteries to KCl or PE showed no significant differences between control and hindlimb unweighting mice. These data indicated that 3 weeks hindlimb unweighting results in a reduced capacity of the arterial smooth muscle of the hindquarter to develop tension. In addition, the alterations in arterial contractile responses caused by hindlimb unweighting in mice are similar as those in rats. Our work suggested that hindlimb unweighting mouse model may be used as a model for the study of postflight cardiovascular deconditioning.

  4. Direct Eulerian MUSCL scheme for gas dynamics

    SciTech Connect

    Colella, P.

    1985-01-01

    The authors present a second order extension of Godunov's method for gas dynamics in Eulerian coordinates patterned after van Leer's MUSCL scheme for gas dynamics in Lagrangian coordinates. The present method performs the Eulerian calculation in a single step by solving Riemann problems and characteristic equations for the fluxes in the Eulerian frame. The authors also make several modifications in the formulation of MUSCL, applicable to both this scheme and to the original Lagrangian scheme, all aimed at making a more robust and accurate scheme. The authors present the results of test calculations in one and two space variables. 12 references, 5 figures.

  5. Fiber-type-specific alphaB-crystallin distribution and its shifts with T(3) and PTU treatments in rat hindlimb muscles.

    PubMed

    Atomi, Y; Toro, K; Masuda, T; Hatta, H

    2000-04-01

    Changes in alphaB-crystallin content in adult rat soleus and extensor digitorum longus (EDL) were examined after 8 wk of 3,5, 3'-triiodothyronine (T(3)) and propylthiouracil (PTU) treatments. Cellular distributions of alphaB-crystallin expression related to fiber type, and distribution shifts with these treatments were also examined in detail from the gray level of reactivity to specific anti-alphaB-crystallin antibody. alphaB-crystallin content in both soleus and EDL muscles was significantly decreased after T(3), and that in EDL was significantly increased over twofold after PTU treatment. In both control soleus and EDL muscles, the gray level of type I fibers was higher than that of type II fibers. alphaB-crystallin expression among type II subtypes was muscle specific; the order was type I > IIa > IIx > IIb in control EDL muscle and type IIx > or = IIa in soleus muscle. The relation was basically unchanged in both muscles after T(3) treatment and was, in particular, well maintained in EDL muscle. Under hypothyroidism conditions with PTU, the mean alphaB-crystallin levels of type IIa and IIx fibers were significantly lower than levels under control conditions. Thus the relation between fiber type and the expression manner of stress protein alphaB-crystallin is muscle specific and also is well regulated under thyroid hormone, especially in fast EDL muscle.

  6. Comparative Sensitivity Analysis of Muscle Activation Dynamics.

    PubMed

    Rockenfeller, Robert; Günther, Michael; Schmitt, Syn; Götz, Thomas

    2015-01-01

    We mathematically compared two models of mammalian striated muscle activation dynamics proposed by Hatze and Zajac. Both models are representative for a broad variety of biomechanical models formulated as ordinary differential equations (ODEs). These models incorporate parameters that directly represent known physiological properties. Other parameters have been introduced to reproduce empirical observations. We used sensitivity analysis to investigate the influence of model parameters on the ODE solutions. In addition, we expanded an existing approach to treating initial conditions as parameters and to calculating second-order sensitivities. Furthermore, we used a global sensitivity analysis approach to include finite ranges of parameter values. Hence, a theoretician striving for model reduction could use the method for identifying particularly low sensitivities to detect superfluous parameters. An experimenter could use it for identifying particularly high sensitivities to improve parameter estimation. Hatze's nonlinear model incorporates some parameters to which activation dynamics is clearly more sensitive than to any parameter in Zajac's linear model. Other than Zajac's model, Hatze's model can, however, reproduce measured shifts in optimal muscle length with varied muscle activity. Accordingly we extracted a specific parameter set for Hatze's model that combines best with a particular muscle force-length relation. PMID:26417379

  7. Simplified and effective motor control based on muscle synergies to exploit musculoskeletal dynamics

    PubMed Central

    Berniker, Max; Jarc, Anthony; Bizzi, Emilio; Tresch, Matthew C.

    2009-01-01

    The basic hypothesis of producing a range of behaviors using a small set of motor commands has been proposed in various forms to explain motor behaviors ranging from basic reflexes to complex voluntary movements. Yet many fundamental questions regarding this long-standing hypothesis remain unanswered. Indeed, given the prominent nonlinearities and high dimensionality inherent in the control of biological limbs, the basic feasibility of a low-dimensional controller and an underlying principle for its creation has remained elusive. We propose a principle for the design of such a controller, that it endeavors to control the natural dynamics of the limb, taking into account the nature of the task being performed. Using this principle, we obtained a low-dimensional model of the hindlimb and a set of muscle synergies to command it. We demonstrate that this set of synergies was capable of producing effective control, establishing the viability of this muscle synergy hypothesis. Finally, by combining the low-dimensional model and the muscle synergies we were able to build a relatively simple controller whose overall performance was close to that of the system's full-dimensional nonlinear controller. Taken together, the results of this study establish that a low-dimensional controller is capable of simplifying control without degrading performance. PMID:19380738

  8. Synchronous monitoring of muscle dynamics and muscle force for maximum isometric tetanus

    NASA Astrophysics Data System (ADS)

    Zakir Hossain, M.; Grill, Wolfgang

    2010-03-01

    Skeletal muscle is a classic example of a biological soft matter . At both macro and microscopic levels, skeletal muscle is exquisitely oriented for force generation and movement. In addition to the dynamics of contracting and relaxing muscle which can be monitored with ultrasound, variations in the muscle force are also expected to be monitored. To observe such force and sideways expansion variations synchronously for the skeletal muscle a novel detection scheme has been developed. As already introduced for the detection of sideways expansion variations of the muscle, ultrasonic transducers are mounted sideways on opposing positions of the monitored muscle. To detect variations of the muscle force, angle of pull of the monitored muscle has been restricted by the mechanical pull of the sonic force sensor. Under this condition, any variation in the time-of-flight (TOF) of the transmitted ultrasonic signals can be introduced by the variation of the path length between the transducers. The observed variations of the TOF are compared to the signals obtained by ultrasound monitoring for the muscle dynamics. The general behavior of the muscle dynamics and muscle force shows almost an identical concept. Since muscle force also relates the psychological boosting-up effects, the influence of boosting-up on muscle force and muscle dynamics can also be quantified form this study. Length-tension or force-length and force-velocity relationship can also be derived quantitatively with such monitoring.

  9. Application of a Rat Hindlimb Model: A Prediction of Force Spaces Reachable Through Stimulation of Nerve Fascicles

    PubMed Central

    Johnson, Will L.; Jindrich, Devin L.; Zhong, Hui; Roy, Roland R.

    2011-01-01

    A device to generate standing or locomotion through chronically placed electrodes has not been fully developed due in part to limitations of clinical experimentation and the high number of muscle activation inputs of the leg. We investigated the feasibility of functional electrical stimulation paradigms that minimize the input dimensions for controlling the limbs by stimulating at nerve fascicles, utilizing a model of the rat hindlimb which combined previously collected morphological data with muscle physiological parameters presented herein. As validation of the model we investigated the suitability of a lumped-parameter model for prediction of muscle activation during dynamic tasks. Using the validated model we found that the space of forces producible through activation of muscle groups sharing common nerve fascicles was nonlinearly dependent on the number of discrete muscle groups that could be individually activated (equivalently, the neuroanatomical level of activation). Seven commonly innervated muscle groups were sufficient to produce 78% of the force space producible through individual activation of the 42 modeled hindlimb muscles. This novel, neuroanatomically derived reduction in input dimension emphasizes the potential to simplify controllers for functional electrical stimulation to improve functional recovery after a neuromuscular injury. PMID:21244999

  10. Pelvic and hindlimb musculature of Tyrannosaurus rex (Dinosauria: Theropoda).

    PubMed

    Carrano, Matthew T; Hutchinson, John R

    2002-09-01

    In this article, we develop a new reconstruction of the pelvic and hindlimb muscles of the large theropod dinosaur Tyrannosaurus rex. Our new reconstruction relies primarily on direct examination of both extant and fossil turtles, lepidosaurs, and archosaurs. These observations are placed into a phylogenetic context and data from extant taxa are used to constrain inferences concerning the soft-tissue structures in T. rex. Using this extant phylogenetic bracket, we are able to offer well-supported inferences concerning most of the hindlimb musculature in this taxon. We also refrain from making any inferences for certain muscles where the resulting optimizations are ambiguous. This reconstruction differs from several previous attempts and we evaluate these discrepancies. In addition to providing a new and more detailed understanding of the hindlimb morphology of T. rex--the largest known terrestrial biped--this reconstruction also helps to clarify the sequence of character-state change along the line to extant birds.

  11. L-Type Voltage-Dependent Calcium Channel Currents of Cerebral Arterial Smooth Muscle Cells are Increased by 2-Week Hindlimb Unweighting in Rats

    NASA Astrophysics Data System (ADS)

    Tang, Hao; Xue, Jun-Hui; Bai, Yun-Gang; Xie, Man-Jiang; Bao, Jun-Xiang; Ma, Jin

    2008-06-01

    To investigate alterations of L-type voltage-dependent calcium channel (CaL) in cerebral vascular smooth muscle cells isolated from rats subjected to a two-week simulated weightlessness, and influence of Bay K 8644 (an agonist of CaL) to the channel currents. Tail-suspended rat model was used to simulate the effects of microgravity. Whole-cell patch-clamp technique was used to record CaL currents before and after Bay K 8644 treatment, with intracellular Ca2+ concentration maintained physiological level. The corresponding parameters such as steady state activation and inactivation curves were also recorded. Whole-cell CaL current densities increased obviously, and sensitivity of CaL to Bay K 8644 also increased in cerebral vascular smooth muscle cells from suspension group. But membrane capacitance (Cm), access resistance (Ra), and other parameters of CaL such as steady state activation / inactivation curves have no significant changes compared with those of control group. These results suggest that enhanced CaL function of cerebrovascular smooth muscle cells induced by simulated microgravity may be one of the electrophysiological mechanisms that mediate enhanced vasoreactivity of cerebrovascular smooth muscle cells during adaptation to simulated weightlessness in rats.

  12. Periodic weight support effects on rat soleus fibers after hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Hauschka, Edward O.; Roy, Roland R.; Edgerton, V. Reggie

    1988-01-01

    The morphological and histochemical properties of rat soleus muscles were investigated following one week of hindlimb suspension. Short-duration daily weight support activity is shown to ameliorate, but not prevent, soleus atrophy induced by hindlimb suspension. The results indicate that fiber cross-sectional area is more responsive to periodic weight support in dark than light ATPas fibers, and that muscle fiber atrophy need not be associated with a loss in succinate dehydrogenase activity.

  13. Loss of distal axons and sensory Merkel cells and features indicative of muscle denervation in hindlimbs of P0-deficient mice.

    PubMed

    Frei, R; Mötzing, S; Kinkelin, I; Schachner, M; Koltzenburg, M; Martini, R

    1999-07-15

    Mice lacking the major Schwann cell myelin component P0 show a severe dysmyelination with pathological features reminiscent of the Déjérine-Sottas syndrome in humans. Previous morphological and electrophysiological studies on these mice did not only demonstrate a compromised myelination and myelin maintenance, but were suggestive of an impairment of axons as well. Here, we studied the axonal pathology in P0-deficient mice by quantitative electron microscopy. In addition, we investigated epidermal receptor end organs by immunocytochemistry and muscle pathology by histochemistry. In proximal sections of facial and femoral nerves, axon calibers were significantly reduced, whereas the number of myelin-competent axons was not diminished in 5- and 17-month-old P0-deficient mice. However, in distal branches of the femoral and sciatic nerve (digital nerves innervating the skin of the first toe) the numbers of myelin-competent axons were reduced by 70% in 6-month-old P0-deficient mice. Immunolabeling of foot pads revealed a corresponding loss of Merkel cells by 75%, suggesting that survival of these cells is dependent on the presence or maintenance of their innervating myelinated axons. In addition, quadriceps and gastrocnemius muscles showed pathological features indicative of denervation and axonal sprouting. These findings demonstrate that loss of an important myelin component can initiate degenerative mechanisms not only in the Schwann cell but also in the distal portions of myelinated axons, leading to the degeneration of specialized receptor end organs and impairment of muscle innervation. PMID:10407042

  14. Modeling the dynamic characteristics of pneumatic muscle.

    PubMed

    Reynolds, D B; Repperger, D W; Phillips, C A; Bandry, G

    2003-03-01

    A pneumatic muscle (PM) system was studied to determine whether a three-element model could describe its dynamics. As far as the authors are aware, this model has not been used to describe the dynamics of PM. A new phenomenological model consists of a contractile (force-generating) element, spring element, and damping element in parallel. The PM system was investigated using an apparatus that allowed precise and accurate actuation pressure (P) control by a linear servo-valve. Length change of the PM was measured by a linear potentiometer. Spring and damping element functions of P were determined by a static perturbation method at several constant P values. These results indicate that at constant P, PM behaves as a spring and damper in parallel. The contractile element function of P was determined by the response to a step input in P, using values of spring and damping elements from the perturbation study. The study showed that the resulting coefficient functions of the three-element model describe the dynamic response to the step input of P accurately, indicating that the static perturbation results can be applied to the dynamic case. This model is further validated by accurately predicting the contraction response to a triangular P waveform. All three elements have pressure-dependent coefficients for pressure P in the range 207 < or = P < or = 621 kPa (30 < or = P < or = 90 psi). Studies with a step decrease in P (relaxation of the PM) indicate that the damping element coefficient is smaller during relaxation than contraction.

  15. Locomotion as an emergent property of muscle contractile dynamics.

    PubMed

    Biewener, Andrew A

    2016-01-01

    Skeletal muscles share many common, highly conserved features of organization at the molecular and myofilament levels, giving skeletal muscle fibers generally similar and characteristic mechanical and energetic properties; properties well described by classical studies of muscle mechanics and energetics. However, skeletal muscles can differ considerably in architectural design (fiber length, pinnation, and connective tissue organization), as well as fiber type, and how they contract in relation to the timing of neuromotor activation and in vivo length change. The in vivo dynamics of muscle contraction is, therefore, crucial to assessing muscle design and the roles that muscles play in animal movement. Architectural differences in muscle-tendon organization combined with differences in the phase of activation and resulting fiber length changes greatly affect the time-varying force and work that muscles produce, as well as the energetic cost of force generation. Intrinsic force-length and force-velocity properties of muscles, together with their architecture, also play important roles in the control of movement, facilitating rapid adjustments to changing motor demands. Such adjustments complement slower, reflex-mediated neural feedback control of motor recruitment. Understanding how individual fiber forces are integrated to whole-muscle forces, which are transmitted to the skeleton for producing and controlling locomotor movement, is therefore essential for assessing muscle design in relation to the dynamics of movement.

  16. Modulation of joint moments and work in the goat hindlimb with locomotor speed and surface grade

    PubMed Central

    Arnold, Allison S.; Lee, David V.; Biewener, Andrew A.

    2013-01-01

    SUMMARY Goats and other quadrupeds must modulate the work output of their muscles to accommodate the changing mechanical demands associated with locomotion in their natural environments. This study examined which hindlimb joint moments goats use to generate and absorb mechanical energy on level and sloped surfaces over a range of locomotor speeds. Ground reaction forces and the three-dimensional locations of joint markers were recorded as goats walked, trotted and galloped over 0, +15 and −15 deg sloped surfaces. Net joint moments, powers and work were estimated at the goats' hip, knee, ankle and metatarsophalangeal joints throughout the stance phase via inverse dynamics calculations. Differences in locomotor speed on the level, inclined and declined surfaces were characterized and accounted for by fitting regression equations to the joint moment, power and work data plotted versus non-dimensionalized speed. During level locomotion, the net work generated by moments at each of the hindlimb joints was small (less than 0.1 J kg−1 body mass) and did not vary substantially with gait or locomotor speed. During uphill running, by contrast, mechanical energy was generated at the hip, knee and ankle, and the net work at each of these joints increased dramatically with speed (P<0.05). The greatest increases in positive joint work occurred at the hip and ankle. During downhill running, mechanical energy was decreased in two main ways: goats generated larger knee extension moments in the first half of stance, absorbing energy as the knee flexed, and goats generated smaller ankle extension moments in the second half of stance, delivering less energy. The goats' hip extension moment in mid-stance was also diminished, contributing to the decrease in energy. These analyses offer new insight into quadrupedal locomotion, clarifying how the moments generated by hindlimb muscles modulate mechanical energy at different locomotor speeds and grades, as needed to accommodate the

  17. Denervation in Femoral Artery-Ligated Hindlimbs Diminishes Ischemic Recovery Primarily via Impaired Arteriogenesis

    PubMed Central

    Qin, Yuansen; Liu, Ruiming; Wang, Huijin; Zhou, Yu; Wang, Shenming; Hu, Zuojun

    2016-01-01

    Aims Multiple factors regulate arteriogenesis. Peripheral nerves play a crucial role in vascular remodeling, but the function of peripheral nerves during arteriogenesis is obscure. Our study investigated the contribution of denervation to arteriogenesis during post-ischemic recovery from hindlimb femoral artery ligation. Methods and Results Sprague-Dawley rats were randomly allocated into four groups of normal control (NC), hindlimb ischemia (HI), hindlimb ischemia with denervation (HID) and hindlimb simple denervation (HD). Hindlimb ischemic recovery was assessed by clinical assessment and tibialis anterior muscle remodeling on day 28 post-surgery. Blood flow was determined by laser Doppler imaging on day 0, 3, 7, 14 and 28 post-surgery. Collateral number of hindlimb was observed by angiography and gracilis muscles were tested by immunostaining on day 7 and 28 post-surgery. Angiogenesis was accessed by counting CD31 positive capillaries in tibialis anterior muscles on day 28 post-surgery. Group HID showed impaired ischemic recovery compared with the other 3 groups and impaired blood flow recovery compared with group HI on day 28 post-surgery. The collateral number and capillary density of group HID were lower than group HI. The collateral diameter of both group HID and group HI significantly increased compared with group NC. However, the lumen diameter was much narrower and the vessel wall was much thicker in group HID than group HI. We also demonstrated that the thickened neointima of collaterals in group HID comprised of smooth muscle cells and endothelial cells. Conclusions Denervation of the ligated femoral artery in the hindlimb impairs ischemic recovery via impaired perfusion. The possible mechanisms of impaired perfusion are lower collateral number, lower capillary density and most likely narrower lumen, which damage ischemic recovery. This study illustrates the crucial role of peripheral nerves in arteriogenesis using a model combined ischemia with

  18. Dynamic strength of the quadriceps muscle and sports activity.

    PubMed

    Hahn, T; Foldspang, A; Ingemann-Hansen, T

    1999-04-01

    The study objectives were to examine the dynamic strength of the quadriceps muscle in athletes, and investigate its association with participation in sport. The study comprised 168 active competitive non-pregnant athletes, aged 14-24 years. The dynamic strength of their quadriceps muscle was measured, and they answered a questionnaire about sports activity and occupation. The dynamic strength of the quadriceps muscle was significantly higher in men than in women, and was positively associated with body weight, years of jogging, years of soccer, and weekly hours of basketball. In conclusion, the dynamic strength of the quadriceps muscle seems to be associated with sports activity. The results suggest sport specific adaptation, which may reflect high levels of running and jumping activity.

  19. Hindlimb unloading: rodent analog for microgravity.

    PubMed

    Globus, Ruth K; Morey-Holton, Emily

    2016-05-15

    The rodent hindlimb unloading (HU) model was developed in the 1980s to make it possible to study mechanisms, responses, and treatments for the adverse consequences of spaceflight. Decades before development of the HU model, weightlessness was predicted to yield deficits in the principal tissues responsible for structure and movement on Earth, primarily muscle and bone. Indeed, results from early spaceflight and HU experiments confirmed the expected sensitivity of the musculoskeletal system to gravity loading. Results from human and animal spaceflight and HU experiments show that nearly all organ systems and tissues studied display some measurable changes, albeit sometimes minor and of uncertain relevance to astronaut health. The focus of this review is to examine key HU results for various organ systems including those related to stress; the immune, cardiovascular, and nervous systems; vision changes; and wound healing. Analysis of the validity of the HU model is important given its potential value for both hypothesis testing and countermeasure development. PMID:26869711

  20. Adynamic and dynamic muscle transposition techniques for anal incontinence

    PubMed Central

    Barišić, Goran; Krivokapić, Zoran

    2014-01-01

    Gracilis muscle transposition is well established in general surgery and has been the main muscle transposition technique for anal incontinence. Dynamization, through a schedule of continuous electrical stimulation, converts the fatigue-prone muscle fibres to a tonic fatigue-resistant morphology with acceptable results in those cases where there is limited sphincter muscle mass. The differences between gluteoplasty and graciloplasty, as well as the techniques and complications of both procedures, are outlined in this review. Overall, these techniques are rarely carried out in specialized units with experience, as there is a high revision and explantation rate. PMID:24759348

  1. Muscle-spring dynamics in time-limited, elastic movements.

    PubMed

    Rosario, M V; Sutton, G P; Patek, S N; Sawicki, G S

    2016-09-14

    Muscle contractions that load in-series springs with slow speed over a long duration do maximal work and store the most elastic energy. However, time constraints, such as those experienced during escape and predation behaviours, may prevent animals from achieving maximal force capacity from their muscles during spring-loading. Here, we ask whether animals that have limited time for elastic energy storage operate with springs that are tuned to submaximal force production. To answer this question, we used a dynamic model of a muscle-spring system undergoing a fixed-end contraction, with parameters from a time-limited spring-loader (bullfrog: Lithobates catesbeiana) and a non-time-limited spring-loader (grasshopper: Schistocerca gregaria). We found that when muscles have less time to contract, stored elastic energy is maximized with lower spring stiffness (quantified as spring constant). The spring stiffness measured in bullfrog tendons permitted less elastic energy storage than was predicted by a modelled, maximal muscle contraction. However, when muscle contractions were modelled using biologically relevant loading times for bullfrog jumps (50 ms), tendon stiffness actually maximized elastic energy storage. In contrast, grasshoppers, which are not time limited, exhibited spring stiffness that maximized elastic energy storage when modelled with a maximal muscle contraction. These findings demonstrate the significance of evolutionary variation in tendon and apodeme properties to realistic jumping contexts as well as the importance of considering the effect of muscle dynamics and behavioural constraints on energy storage in muscle-spring systems. PMID:27629031

  2. Muscle-spring dynamics in time-limited, elastic movements.

    PubMed

    Rosario, M V; Sutton, G P; Patek, S N; Sawicki, G S

    2016-09-14

    Muscle contractions that load in-series springs with slow speed over a long duration do maximal work and store the most elastic energy. However, time constraints, such as those experienced during escape and predation behaviours, may prevent animals from achieving maximal force capacity from their muscles during spring-loading. Here, we ask whether animals that have limited time for elastic energy storage operate with springs that are tuned to submaximal force production. To answer this question, we used a dynamic model of a muscle-spring system undergoing a fixed-end contraction, with parameters from a time-limited spring-loader (bullfrog: Lithobates catesbeiana) and a non-time-limited spring-loader (grasshopper: Schistocerca gregaria). We found that when muscles have less time to contract, stored elastic energy is maximized with lower spring stiffness (quantified as spring constant). The spring stiffness measured in bullfrog tendons permitted less elastic energy storage than was predicted by a modelled, maximal muscle contraction. However, when muscle contractions were modelled using biologically relevant loading times for bullfrog jumps (50 ms), tendon stiffness actually maximized elastic energy storage. In contrast, grasshoppers, which are not time limited, exhibited spring stiffness that maximized elastic energy storage when modelled with a maximal muscle contraction. These findings demonstrate the significance of evolutionary variation in tendon and apodeme properties to realistic jumping contexts as well as the importance of considering the effect of muscle dynamics and behavioural constraints on energy storage in muscle-spring systems.

  3. Circulating protein synthesis rates reveal skeletal muscle proteome dynamics

    PubMed Central

    Shankaran, Mahalakshmi; King, Chelsea L.; Angel, Thomas E.; Holmes, William E.; Li, Kelvin W.; Colangelo, Marc; Price, John C.; Turner, Scott M.; Bell, Christopher; Hamilton, Karyn L.; Miller, Benjamin F.; Hellerstein, Marc K.

    2015-01-01

    Here, we have described and validated a strategy for monitoring skeletal muscle protein synthesis rates in rodents and humans over days or weeks from blood samples. We based this approach on label incorporation into proteins that are synthesized specifically in skeletal muscle and escape into the circulation. Heavy water labeling combined with sensitive tandem mass spectrometric analysis allowed integrated synthesis rates of proteins in muscle tissue across the proteome to be measured over several weeks. Fractional synthesis rate (FSR) of plasma creatine kinase M-type (CK-M) and carbonic anhydrase 3 (CA-3) in the blood, more than 90% of which is derived from skeletal muscle, correlated closely with FSR of CK-M, CA-3, and other proteins of various ontologies in skeletal muscle tissue in both rodents and humans. Protein synthesis rates across the muscle proteome generally changed in a coordinate manner in response to a sprint interval exercise training regimen in humans and to denervation or clenbuterol treatment in rodents. FSR of plasma CK-M and CA-3 revealed changes and interindividual differences in muscle tissue proteome dynamics. In human subjects, sprint interval training primarily stimulated synthesis of structural and glycolytic proteins. Together, our results indicate that this approach provides a virtual biopsy, sensitively revealing individualized changes in proteome-wide synthesis rates in skeletal muscle without a muscle biopsy. Accordingly, this approach has potential applications for the diagnosis, management, and treatment of muscle disorders. PMID:26657858

  4. Dynamic Regulation of Sarcomeric Actin Filaments in Striated Muscle

    PubMed Central

    Ono, Shoichiro

    2010-01-01

    In striated muscle, the actin cytoskeleton is differentiated into myofibrils. Actin and myosin filaments are organized in sarcomeres and specialized for producing contractile forces. Regular arrangement of actin filaments with uniform length and polarity is critical for the contractile function. However, the mechanisms of assembly and maintenance of sarcomeric actin filaments in striated muscle are not completely understood. Live imaging of actin in striated muscle has revealed that actin subunits within sarcomeric actin filaments are dynamically exchanged without altering overall sarcomeric structures. A number of regulators for actin dynamics have been identified, and malfunction of these regulators often result in disorganization of myofibril structures or muscle diseases. Therefore, proper regulation of actin dynamics in striated muscle is critical for assembly and maintenance of functional myofibrils. Recent studies have suggested that both enhancers of actin dynamics and stabilizers of actin filaments are important for sarcomeric actin organization. Further investigation of the regulatory mechanism of actin dynamics in striated muscle should be a key to understanding how myofibrils develop and operate. © 2010 Wiley-Liss, Inc. PMID:20737540

  5. Building a robotic link between muscle dynamics and hydrodynamics.

    PubMed

    Richards, Christopher T

    2011-07-15

    This study used a novel feedback approach to control a robotic foot using force and length signals transmitted from an isolated Xenopus laevis frog muscle. The foot's environment (inertial versus hydrodynamic), gearing (outlever/inlever) and size were changed to alter the muscle's load. Upon nerve stimulation (250 Hz, 80 ms train duration), variation in loading generated a range of muscle stress (19.8±5.3 to 66.0±22.5 kPa), work (1.89±0.67 to 6.87±2.96 J kg(-1) muscle) and power (12.4±7.5 to 64.8±28.3 W kg(-1) muscle; mean ± s.d., N=6 frogs). Inertial versus hydrodynamic loading dramatically shifted contractile dynamics. With the foot in water, the muscle generated ∼30% higher force, yet shortened slower, producing lower power than inertial loading. Power increased in air from 22.6±5.8 to 63.6±27.2 W kg(-1) muscle in response to doubling the gear ratio, but did not increase in water. Surprisingly, altering foot size diminished muscle performance in water, causing power to drop significantly from 41.6±11.1 to 25.1±8.0 W kg(-1) muscle as foot area was doubled. Thus, morphological modifications influenced muscle dynamics independently of neural control; however, changes in loading environment and gearing affected contractile output more strongly than changes in foot size. Confirming recent theory, these findings demonstrate how muscle contractile output can be modulated solely by altering the mechanical environment.

  6. Effects of hindlimb unloading on neuromuscular development of neonatal rats

    NASA Technical Reports Server (NTRS)

    Huckstorf, B. L.; Slocum, G. R.; Bain, J. L.; Reiser, P. M.; Sedlak, F. R.; Wong-Riley, M. T.; Riley, D. A.

    2000-01-01

    We hypothesized that hindlimb suspension unloading of 8-day-old neonatal rats would disrupt the normal development of muscle fiber types and the motor innervation of the antigravity (weightbearing) soleus muscles but not extensor digitorum longus (EDL) muscles. Five rats were suspended 4.5 h and returned 1.5 h to the dam for nursing on a 24 h cycle for 9 days. To control for isolation from the dam, the remaining five littermates were removed on the same schedule but not suspended. Another litter of 10 rats housed in the same room provided a vivarium control. Fibers were typed by myofibrillar ATPase histochemistry and immunostaining for embryonic, slow, fast IIA and fast IIB isomyosins. The percentage of multiple innervation and the complexity of singly-innervated motor terminal endings were assessed in silver/cholinesterase stained sections. Unique to the soleus, unloading accelerated production of fast IIA myosin, delayed expression of slow myosin and retarded increases in standardized muscle weight and fiber size. Loss of multiple innervation was not delayed. However, fewer than normal motor nerve endings achieved complexity. Suspended rats continued unloaded hindlimb movements. These findings suggest that motor neurons resolve multiple innervation through nerve impulse activity, whereas the postsynaptic element (muscle fiber) controls endplate size, which regulates motor terminal arborization. Unexpectedly, in the EDL of unloaded rats, transition from embryonic to fast myosin expression was retarded. Suspension-related foot drop, which stretches and chronically loads EDL, may have prevented fast fiber differentiation. These results demonstrate that neuromuscular development of both weightbearing and non-weightbearing muscles in rats is dependent upon and modulated by hindlimb loading.

  7. Gait kinematic analysis evaluates hindlimb revascularization.

    PubMed

    Ríos, Amelia; Delgado, Alexandra; Escalante, Bruno; Santana, Jesús

    2011-01-01

    Peripheral arterial occlusive disease is described as vascular disorders associated with ischemia and may be the result of an obstructive vascular process or a lost revascularization response. We have shown that gait locomotion analysis by video filming represents an integrative model for the evaluation of mechanisms involved in the process of ischemia-induced revascularization. However, analysis by this method can be subjective and perception errors may be occurring. We present the optimization of a quantifiable, noninvasive, reproducible method that analyzes ankle kinematics in rats using a two-dimensional digital video system. Gait dynamics were filmed in hindlimb ischemic rats with a high speed digital video camera. Images were collected and analyzed at 125 frames per second. An algorithm using interactive data language (IDL) was devised to assess different parameters. In ischemic rats, stride time and knee joint angle remained altered 10 days post-surgery compared with sham animals. Gait kinematics were outlined in a highly reliable way by this computational analysis and corroborated the notion of hindlimb movement recovery associated with the revascularization process.

  8. Muscle Lim Protein isoform negatively regulates striated muscle actin dynamics and differentiation

    PubMed Central

    Vafiadaki, Elizabeth; Arvanitis, Demetrios A.; Papalouka, Vasiliki; Terzis, Gerasimos; Roumeliotis, Theodoros I.; Spengos, Konstantinos; Garbis, Spiros D.; Manta, Panagiota; Kranias, Evangelia G.; Sanoudou, Despina

    2015-01-01

    Muscle Lim Protein (MLP) has emerged as a critical regulator of striated muscle physiology and pathophysiology. Mutations in cysteine and glycine-rich protein 3 (CSRP3), the gene encoding MLP, have been directly associated with human cardiomyopathies, while aberrant expression patterns are reported in human cardiac and skeletal muscle diseases. Increasing evidence suggests that MLP has an important role in both myogenic differentiation and myocyte cytoarchitecture, although the full spectrum of its intracellular roles has not been delineated. We report the discovery of an alternative splice variant of MLP, designated as MLP-b, showing distinct expression in neuromuscular disease and direct roles in actin dynamics and muscle differentiation. This novel isoform originates by alternative splicing of exons 3 and 4. At the protein level, it contains the N-terminus first half LIM domain of MLP and a unique sequence of 22 amino acids. Physiologically it is expressed during early differentiation, whereas its overexpression reduces C2C12 differentiation and myotube formation. This may be mediated through its inhibition of MLP/CFL2-mediated F-actin dynamics. In differentiated striated muscles, MLP-b localizes to the sarcomeres and binds directly to Z-disc components including α-actinin, T-cap and MLP. Our findings unveil a novel player in muscle physiology and pathophysiology that is implicated in myogenesis as a negative regulator of myotube formation, and in differentiated striated muscles as a contributor to sarcomeric integrity. PMID:24860983

  9. Ankle muscle strength influence on muscle activation during dynamic and static ankle training modalities.

    PubMed

    Lucas-Cuevas, Angel Gabriel; Baltich, Jennifer; Enders, Hendrik; Nigg, Sandro; Nigg, Benno

    2016-01-01

    Muscle weakness is considered a risk factor for ankle injury. Balance training and barefoot running have been used in an attempt to strengthen the muscles crossing the ankle. It is expected that training tasks that successfully strengthen the ankle would elicit increased muscular activity. However, it is unknown how an individual's ankle strength will influence the muscle activity used during a given task. Twenty-six participants performed dynamic (shod, barefoot running) and static tasks (squat on ground, squat on ®Bosu Ball) believed to strengthen the muscles surrounding the ankle. Electromyographic signals of the tibialis anterior, peroneus longus, gastrocnemius lateralis (GL) and gastrocnemius medialis (GM) were recorded and analysed using a non-linearly scaled wavelet analysis. Participants were divided into a strong group and a weak group according to their isometric plantar-flexion torque. The weak group required more relative GL and GM muscle activity during each training task compared to the strong group. No difference was observed between shod and barefoot running. There was a significant effect of training task on muscle activation level for the weak group. Differences in ankle strength had a significant impact on muscle activation.

  10. DNA methylation dynamics in muscle development and disease

    PubMed Central

    Carrió, Elvira; Suelves, Mònica

    2015-01-01

    DNA methylation is an essential epigenetic modification for mammalian development and is crucial for the establishment and maintenance of cellular identity. Traditionally, DNA methylation has been considered as a permanent repressive epigenetic mark. However, the application of genome-wide approaches has allowed the analysis of DNA methylation in different genomic contexts revealing a more dynamic regulation than originally thought, since active DNA methylation and demethylation occur during cellular differentiation and tissue specification. Satellite cells are the primary stem cells in adult skeletal muscle and are responsible for postnatal muscle growth, hypertrophy, and muscle regeneration. This review outlines the published data regarding DNA methylation changes along the skeletal muscle program, in both physiological and pathological conditions, to better understand the epigenetic mechanisms that control myogenesis. PMID:25798107

  11. A simple hindlimb suspension apparatus

    NASA Technical Reports Server (NTRS)

    Park, E.; Schultz, E.

    1993-01-01

    This paper describes the assembly of a simple, inexpensive apparatus for application of the hindlimb suspension model to studies of the effects of unloading on mammalian physiology. Construction of a cage and suspension assembly is described using materials that can be obtained from most hardware stores. The design is kept simple for easy assembly and disassembly to facilitate cleaning and storage. The suspension assembly allows the animals full access to all portions of the floor area and provides an effective environment to study the effects of unloading.

  12. Increased serotonergic innervation of lumbosacral motoneurons of rolling mouse Nagoya in correlation with abnormal hindlimb extension.

    PubMed

    Koyanagi, Y; Sawada, K; Sakata-Haga, H; Jeong, Y-G; Fukui, Y

    2006-12-01

    Rolling Mouse Nagoya (RMN) carries a mutation in a gene encoding for alpha(1A) subunit of P/Q-type Ca(2+) channel (Ca(v)2.1). In addition to ataxia, this mutant mouse exhibits abnormal hindlimb extension, which is characterized by a sustained excessive tone of hindlimb extensor muscles. This study aimed to clarify whether serotonergic (5-HTergic) innervation of the spinal motoneurons was altered in RMN in relation to the abnormal hindlimb extension. The density of 5-HT immunoreactive fibres in the ventral horn of lumbar and sacral regions of spinal cord was significantly greater in RMN than in controls. Retrograde wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) labelling combined with 5-HT immunostaining revealed that the number of 5-HT immunoreactive terminals adjoining femoris quadriceps motoneurons was about 2.5-fold greater in RMN than in controls. Furthermore, 5-HT immunostaining in the lumbar cord ventral horn was examined in three other Ca(v)2.1 mutant mice (tottering, leaner and pogo) as to whether or not they showed the abnormal hindlimb extension. Among these mutants, the increased density of 5-HT immunoreactive fibres was observed in correlation with the presence of the abnormal hindlimb extension. The results suggest an increased 5-HTergic innervation of the lumbosacral motoneurons in correlation with the abnormal hindlimb extension in RMN and other Ca(v)2.1 mutant mice. As 5-HT is known to induce the sustained membrane depolarizations without continuous excitatory synaptic inputs (plateau potentials) in spinal motoneurons, the increased 5-HTergic innervation may cause the sustained excitation of hindlimb extensor motoneurons, resulting in the abnormal hindlimb extension.

  13. Dynamics of the Skeletal Muscle Secretome during Myoblast Differentiation*

    PubMed Central

    Henningsen, Jeanette; Rigbolt, Kristoffer T. G.; Blagoev, Blagoy; Pedersen, Bente Klarlund; Kratchmarova, Irina

    2010-01-01

    During recent years, increased efforts have focused on elucidating the secretory function of skeletal muscle. Through secreted molecules, skeletal muscle affects local muscle biology in an auto/paracrine manner as well as having systemic effects on other tissues. Here we used a quantitative proteomics platform to investigate the factors secreted during the differentiation of murine C2C12 skeletal muscle cells. Using triple encoding stable isotope labeling by amino acids in cell culture, we compared the secretomes at three different time points of muscle differentiation and followed the dynamics of protein secretion. We identified and quantitatively analyzed 635 secreted proteins, including 35 growth factors, 40 cytokines, and 36 metallopeptidases. The extensive presence of these proteins that can act as potent signaling mediators to other cells and tissues strongly highlights the important role of the skeletal muscle as a prominent secretory organ. In addition to previously reported molecules, we identified many secreted proteins that have not previously been shown to be released from skeletal muscle cells nor shown to be differentially released during the process of myogenesis. We found 188 of these secreted proteins to be significantly regulated during the process of myogenesis. Comparative analyses of selected secreted proteins revealed little correlation between their mRNA and protein levels, indicating pronounced regulation by posttranscriptional mechanisms. Furthermore, analyses of the intracellular levels of members of the semaphorin family and their corresponding secretion dynamics demonstrated that the release of secreted proteins is tightly regulated by the secretory pathway, the stability of the protein, and/or the processing of secreted proteins. Finally, we provide 299 unique hydroxyproline sites mapping to 48 distinct secreted proteins and have discovered a novel hydroxyproline motif. PMID:20631206

  14. Quantitative changes of GABA-immunoreactive cells in the hindlimb representation of the rat somatosensory cortex after 14-day hindlimb unloading by tail suspension

    NASA Technical Reports Server (NTRS)

    D'Amelio, F.; Fox, R. A.; Wu, L. C.; Daunton, N. G.

    1996-01-01

    The present study was aimed at evaluating quantitatively gamma-aminobutyric acid (GABA) immunoreactivity in the hindlimb representation of the rat somatosensory cortex after 14 days of hindlimb unloading by tail suspension. A reduction in the number of GABA-immunoreactive cells with respect to the control animals was observed in layer Va and Vb. GABA-containing terminals were also reduced in the same layers, particularly those terminals surrounding the soma and apical dendrites of pyramidal cells in layer Vb. On the basis of previous morphological and behavioral studies of the neuromuscular system of hindlimb-suspended animals, it is suggested that the unloading due to hindlimb suspension alters afferent signaling and feedback information from intramuscular receptors to the cerebral cortex due to modifications in the reflex organization of hindlimb muscle groups. We propose that the reduction in immunoreactivity of local circuit GABAergic neurons and terminals is an expression of changes in their modulatory activity to compensate for the alterations in the afferent information.

  15. Mechanisms underlying rhythmic locomotion: dynamics of muscle activation

    PubMed Central

    Chen, Jun; Tian, Jianghong; Iwasaki, Tetsuya; Friesen, W. Otto

    2011-01-01

    SUMMARY We have studied the dynamical properties of tension development in leech longitudinal muscle during swimming. A new method is proposed for modeling muscle properties under functionally relevant conditions where the muscle is subjected to both periodic activation and rhythmic length changes. The ‘dual-sinusoid’ experiments were conducted on preparations of leech nerve cord and body wall. The longitudinal muscle was activated periodically by injection of sinusoidal currents into an identified motoneuron. Simultaneously, sinusoidal length changes were imposed on the body wall with prescribed phase differences (12 values equally spaced over 2π radians) with respect to the current injection. Through the singular value decomposition of appropriately constructed tension data matrices, the leech muscle was found to have a multiplicative structure in which the tension was expressed as the product of activation and length factors. The time courses of activation and length factors were determined from the tension data and were used to develop component models. The proposed modeling method is a general one and is applicable to contractile elements for which the effects of series elasticity are negligible. PMID:21562183

  16. Prediction of muscle performance during dynamic repetitive movement

    NASA Technical Reports Server (NTRS)

    Byerly, D. L.; Byerly, K. A.; Sognier, M. A.; Squires, W. G.

    2003-01-01

    BACKGROUND: During long-duration spaceflight, astronauts experience progressive muscle atrophy and often perform strenuous extravehicular activities. Post-flight, there is a lengthy recovery period with an increased risk for injury. Currently, there is a critical need for an enabling tool to optimize muscle performance and to minimize the risk of injury to astronauts while on-orbit and during post-flight recovery. Consequently, these studies were performed to develop a method to address this need. METHODS: Eight test subjects performed a repetitive dynamic exercise to failure at 65% of their upper torso weight using a Lordex spinal machine. Surface electromyography (SEMG) data was collected from the erector spinae back muscle. The SEMG data was evaluated using a 5th order autoregressive (AR) model and linear regression analysis. RESULTS: The best predictor found was an AR parameter, the mean average magnitude of AR poles, with r = 0.75 and p = 0.03. This parameter can predict performance to failure as early as the second repetition of the exercise. CONCLUSION: A method for predicting human muscle performance early during dynamic repetitive exercise was developed. The capability to predict performance to failure has many potential applications to the space program including evaluating countermeasure effectiveness on-orbit, optimizing post-flight recovery, and potential future real-time monitoring capability during extravehicular activity.

  17. Directional constraint of endpoint force emerges from hindlimb anatomy.

    PubMed

    Bunderson, Nathan E; McKay, J Lucas; Ting, Lena H; Burkholder, Thomas J

    2010-06-15

    Postural control requires the coordination of force production at the limb endpoints to apply an appropriate force to the body. Subjected to horizontal plane perturbations, quadruped limbs stereotypically produce force constrained along a line that passes near the center of mass. This phenomenon, referred to as the force constraint strategy, may reflect mechanical constraints on the limb or body, a specific neural control strategy or an interaction among neural controls and mechanical constraints. We used a neuromuscular model of the cat hindlimb to test the hypothesis that the anatomical constraints restrict the mechanical action of individual muscles during stance and constrain the response to perturbations to a line independent of perturbation direction. In a linearized neuromuscular model of the cat hindlimb, muscle lengthening directions were highly conserved across 10,000 different muscle activation patterns, each of which produced an identical, stance-like endpoint force. These lengthening directions were closely aligned with the sagittal plane and reveal an anatomical structure for directionally constrained force responses. Each of the 10,000 activation patterns was predicted to produce stable stance based on Lyapunov stability analysis. In forward simulations of the nonlinear, seven degree of freedom model under the action of 200 random muscle activation patterns, displacement of the endpoint from its equilibrium position produced restoring forces, which were also biased toward the sagittal plane. The single exception was an activation pattern based on minimum muscle stress optimization, which produced destabilizing force responses in some perturbation directions. The sagittal force constraint increased during simulations as the system shifted from an inertial response during the acceleration phase to a viscoelastic response as peak velocity was obtained. These results qualitatively match similar experimental observations and suggest that the force

  18. Biomedical analysis of rat body hair after hindlimb suspension for 14 days

    NASA Astrophysics Data System (ADS)

    Terada, Masahiro; Kawano, Fuminori; Ishioka, Noriaki; Higashibata, Akira; Majima, Hideyuki J.; Yamazaki, Takashi; Watanabe-Asaka, Tomomi; Niihori, Maki; Nakao, Reiko; Yamada, Shin; Mukai, Chiaki; Ohira, Yoshinobu

    2012-04-01

    The levels of 26 minerals in rat body hair were analyzed in control and hindlimb-suspended Wistar Hannover rats (n=5 each). We quantified the levels of 22 minerals in this experiment. However, we were unable to measure the levels of 4 minerals (Be, V, Cd, and Hg) quantitatively because they were below the limit of detection. Of the 22 quantified, the levels of 19 minerals were not significantly different between control and hindlimb-suspended groups. The levels of 3 minerals (Pb, Cr, and Al) tended to be higher in the hindlimb-suspended group than in the control group; however, this difference was not significant. The concentrations of 3 other minerals (I, K, and Mg) were significantly different between the 2 groups. The iodine (I) level was 58.2% higher in the hindlimb-suspended group than in the control group (P<0.05). Potassium (K) and magnesium (Mg) levels were 55.2% and 20.4% lower, respectively, in the experimental group (P<0.05 in both cases). These results indicate that a physiological change in mineral metabolism resulting from physical or mental stress, such as hindlimb suspension, is reflected in body hair. The Japan Aerospace Exploration Agency (JAXA) has initiated a human research study to investigate the effects of long-term space flight on gene expression and mineral metabolism by analyzing hair samples of astronauts who stayed in the International Space Station (ISS) for 6 months. We believe that hindlimb suspension for 14 days can simulate the effects of an extremely severe environment, such as space flight, because the hindlimb suspension model elicits a rapid physiological change in skeletal muscle, bone, and fluid shift even in the short term. These results also suggest that we can detect various effects on the body by analyzing the human scalp hair shaft.

  19. Functional anatomy of the cheetah (Acinonyx jubatus) hindlimb.

    PubMed

    Hudson, Penny E; Corr, Sandra A; Payne-Davis, Rachel C; Clancy, Sinead N; Lane, Emily; Wilson, Alan M

    2011-04-01

    The cheetah is capable of a top speed of 29 ms(-1) compared to the maximum speed of 17 ms(-1) achieved by the racing greyhound. In this study of the hindlimb and in the accompanying paper on the forelimb we have quantified the musculoskeletal anatomy of the cheetah and greyhound and compared them to identify any differences that may account for this variation in their locomotor abilities. Specifically, bone length, mass and mid-shaft diameter were measured, along with muscle mass, fascicle lengths, pennation angles and moment arms to enable estimates of maximal isometric force, joint torques and joint rotational velocities to be calculated. Surprisingly the cheetahs had a smaller volume of hip extensor musculature than the greyhounds, and we therefore propose that the cheetah powers acceleration using its extensive back musculature. The cheetahs also had an extremely powerful psoas muscle which could help to resist the pitching moments around the hip associated with fast accelerations. The hindlimb bones were proportionally longer and heavier, enabling the cheetah to take longer strides and potentially resist higher peak limb forces. The cheetah therefore possesses several unique adaptations for high-speed locomotion and fast accelerations, when compared to the racing greyhound.

  20. Functional anatomy of the cheetah (Acinonyx jubatus) hindlimb

    PubMed Central

    Hudson, Penny E; Corr, Sandra A; Payne-Davis, Rachel C; Clancy, Sinead N; Lane, Emily; Wilson, Alan M

    2011-01-01

    The cheetah is capable of a top speed of 29 ms−1 compared to the maximum speed of 17 ms−1 achieved by the racing greyhound. In this study of the hindlimb and in the accompanying paper on the forelimb we have quantified the musculoskeletal anatomy of the cheetah and greyhound and compared them to identify any differences that may account for this variation in their locomotor abilities. Specifically, bone length, mass and mid-shaft diameter were measured, along with muscle mass, fascicle lengths, pennation angles and moment arms to enable estimates of maximal isometric force, joint torques and joint rotational velocities to be calculated. Surprisingly the cheetahs had a smaller volume of hip extensor musculature than the greyhounds, and we therefore propose that the cheetah powers acceleration using its extensive back musculature. The cheetahs also had an extremely powerful psoas muscle which could help to resist the pitching moments around the hip associated with fast accelerations. The hindlimb bones were proportionally longer and heavier, enabling the cheetah to take longer strides and potentially resist higher peak limb forces. The cheetah therefore possesses several unique adaptations for high-speed locomotion and fast accelerations, when compared to the racing greyhound. PMID:21062282

  1. Methods for Acute and Subacute Murine Hindlimb Ischemia.

    PubMed

    Padgett, Michael E; McCord, Timothy J; McClung, Joseph M; Kontos, Christopher D

    2016-01-01

    Peripheral artery disease (PAD) is a leading cause of cardiovascular morbidity and mortality in developed countries, and animal models that reliably reproduce the human disease are necessary to develop new therapies for this disease. The mouse hindlimb ischemia model has been widely used for this purpose, but the standard practice of inducing acute limb ischemia by ligation of the femoral artery can result in substantial tissue necrosis, compromising investigators' ability to study the vascular and skeletal muscle tissue responses to ischemia. An alternative approach to femoral artery ligation is the induction of gradual femoral artery occlusion through the use of ameroid constrictors. When placed around the femoral artery in the same or different locations as the sites of femoral artery ligation, these devices occlude the artery over 1 - 3 days, resulting in more gradual, subacute ischemia. This results in less substantial skeletal muscle tissue necrosis, which may more closely mimic the responses seen in human PAD. Because genetic background influences outcomes in both the acute and subacute ischemia models, consideration of the mouse strain being studied is important in choosing the best model. This paper describes the proper procedure and anatomical placement of ligatures or ameroid constrictors on the mouse femoral artery to induce subacute or acute hindlimb ischemia in the mouse. PMID:27403963

  2. The hindlimb myology of Milvago chimango (Polyborinae, Falconidae).

    PubMed

    Mosto, María Clelia; Carril, Julieta; Picasso, Mariana Beatriz Julieta

    2013-10-01

    We describe the hindlimb myology of Milvago chimango. This member of the Falconidae: Polyborinae is a generalist and opportunist that can jump and run down prey on the ground, unlike Falconinae that hunt birds in flight and kill them by striking with its talons. Due to differences in the locomotion habits between the subfamilies, we hypothesized differences in their hindlimb myology. Gross dissections showed that the myology of M. chimango is concordant with that described of other falconids, except for the following differences: the m. flexor cruris medialis has one belly with a longitudinal division; the m. iliotibialis lateralis does not have a connection with the m. iliofibularis; the m. fibularis longus is strongly aponeurotic; the m. tibialis cranialis lacks an accessory tendons and the m. flexor hallucis longus has one place of origin, instead of two. The presence of the m. flexor cruris lateralis can be distinguished as it has been described absent for the Falconidae. We associated its presence with the predominant terrestrial habit of the M. chimango. Each muscle dissected was weighed and the relationship between flexors and extensors at each joint was assessed. The extensor muscles predominated in all joints in M. chimango. Among the flexors, the m. flexor hallucis longus was the heaviest, which could be related to the importance of the use of its talons to obtain food.

  3. Methods for Acute and Subacute Murine Hindlimb Ischemia

    PubMed Central

    Padgett, Michael E.; McCord, Timothy J.; McClung, Joseph M.; Kontos, Christopher D.

    2016-01-01

    Peripheral artery disease (PAD) is a leading cause of cardiovascular morbidity and mortality in developed countries, and animal models that reliably reproduce the human disease are necessary to develop new therapies for this disease. The mouse hindlimb ischemia model has been widely used for this purpose, but the standard practice of inducing acute limb ischemia by ligation of the femoral artery can result in substantial tissue necrosis, compromising investigators' ability to study the vascular and skeletal muscle tissue responses to ischemia. An alternative approach to femoral artery ligation is the induction of gradual femoral artery occlusion through the use of ameroid constrictors. When placed around the femoral artery in the same or different locations as the sites of femoral artery ligation, these devices occlude the artery over 1-3 days, resulting in more gradual, subacute ischemia. This results in less substantial skeletal muscle tissue necrosis, which may more closely mimic the responses seen in human PAD. Because genetic background influences outcomes in both the acute and subacute ischemia models, consideration of the mouse strain being studied is important in choosing the best model. This paper describes the proper procedure and anatomical placement of ligatures or ameroid constrictors on the mouse femoral artery to induce subacute or acute hindlimb ischemia in the mouse. PMID:27403963

  4. Effects of isoproterenol infusion on the hindlimb metabolism of growing wether lambs.

    PubMed

    Brown, J; Crompton, L A; Lomax, M A

    1991-01-01

    The effect of a mixed beta 1/beta 2-adrenergic agonist, isoproterenol, on hindlimb metabolism was studied in growing wether lambs using arteriovenous difference and blood flow rate techniques. Isoproterenol (48 micrograms kg-1 d-1), or saline, was infused into a jugular vein of five wether lambs (30 to 35 kg) for five days and samples taken on the fifth day of treatment. Infusion of isoproterenol significantly increased blood flow, oxygen uptake and tyrosine uptake across the hindlimb. Hindlimb non-esterified fatty acid uptake was increased but not significantly (P = 0.11) and arterial growth hormone concentration was not altered by isoproterenol infusion. Results suggest that beta-adrenergic agonists promote lean tissue deposition by increased muscle blood flow rate and amino acid uptake.

  5. Multivariable Dynamic Ankle Mechanical Impedance With Active Muscles

    PubMed Central

    Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

    2015-01-01

    Multivariable dynamic ankle mechanical impedance in two coupled degrees-of-freedom (DOFs) was quantified when muscles were active. Measurements were performed at five different target activation levels of tibialis anterior and soleus, from 10% to 30% of maximum voluntary contraction (MVC) with increments of 5% MVC. Interestingly, several ankle behaviors characterized in our previous study of the relaxed ankle were observed with muscles active: ankle mechanical impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness; stiffness was greater in the sagittal plane than in the frontal plane at all activation conditions for all subjects; and the coupling between dorsiflexion–plantarflexion and inversion–eversion was small—the two DOF measurements were well explained by a strictly diagonal impedance matrix. In general, ankle stiffness increased linearly with muscle activation in all directions in the 2-D space formed by the sagittal and frontal planes, but more in the sagittal than in the frontal plane, resulting in an accentuated “peanut shape.” This characterization of young healthy subjects’ ankle mechanical impedance with active muscles will serve as a baseline to investigate pathophysiological ankle behaviors of biomechanically and/or neurologically impaired patients. PMID:25203497

  6. Feasible muscle activation ranges based on inverse dynamics analyses of human walking.

    PubMed

    Simpson, Cole S; Sohn, M Hongchul; Allen, Jessica L; Ting, Lena H

    2015-09-18

    Although it is possible to produce the same movement using an infinite number of different muscle activation patterns owing to musculoskeletal redundancy, the degree to which observed variations in muscle activity can deviate from optimal solutions computed from biomechanical models is not known. Here, we examined the range of biomechanically permitted activation levels in individual muscles during human walking using a detailed musculoskeletal model and experimentally-measured kinetics and kinematics. Feasible muscle activation ranges define the minimum and maximum possible level of each muscle's activation that satisfy inverse dynamics joint torques assuming that all other muscles can vary their activation as needed. During walking, 73% of the muscles had feasible muscle activation ranges that were greater than 95% of the total muscle activation range over more than 95% of the gait cycle, indicating that, individually, most muscles could be fully active or fully inactive while still satisfying inverse dynamics joint torques. Moreover, the shapes of the feasible muscle activation ranges did not resemble previously-reported muscle activation patterns nor optimal solutions, i.e. static optimization and computed muscle control, that are based on the same biomechanical constraints. Our results demonstrate that joint torque requirements from standard inverse dynamics calculations are insufficient to define the activation of individual muscles during walking in healthy individuals. Identifying feasible muscle activation ranges may be an effective way to evaluate the impact of additional biomechanical and/or neural constraints on possible versus actual muscle activity in both normal and impaired movements.

  7. Mesenchymal Stem Cells Enhance Nerve Regeneration in a Rat Sciatic Nerve Repair and Hindlimb Transplant Model

    PubMed Central

    Cooney, Damon S.; Wimmers, Eric G.; Ibrahim, Zuhaib; Grahammer, Johanna; Christensen, Joani M.; Brat, Gabriel A.; Wu, Lehao W.; Sarhane, Karim A.; Lopez, Joseph; Wallner, Christoph; Furtmüller, Georg J.; Yuan, Nance; Pang, John; Sarkar, Kakali; Lee, W. P. Andrew; Brandacher, Gerald

    2016-01-01

    This study investigates the efficacy of local and intravenous mesenchymal stem cell (MSC) administration to augment neuroregeneration in both a sciatic nerve cut-and-repair and rat hindlimb transplant model. Bone marrow-derived MSCs were harvested and purified from Brown-Norway (BN) rats. Sciatic nerve transections and repairs were performed in three groups of Lewis (LEW) rats: negative controls (n = 4), local MSCs (epineural) injection (n = 4), and systemic MSCs (intravenous) injection (n = 4). Syngeneic (LEW-LEW) (n = 4) and allogeneic (BN-LEW) (n = 4) hindlimb transplants were performed and assessed for neuroregeneration after local or systemic MSC treatment. Rats undergoing sciatic nerve cut-and-repair and treated with either local or systemic injection of MSCs had significant improvement in the speed of recovery of compound muscle action potential amplitudes and axon counts when compared with negative controls. Similarly, rats undergoing allogeneic hindlimb transplants treated with local injection of MSCs exhibited significantly increased axon counts. Similarly, systemic MSC treatment resulted in improved nerve regeneration following allogeneic hindlimb transplants. Systemic administration had a more pronounced effect on electromotor recovery while local injection was more effective at increasing fiber counts, suggesting different targets of action. Local and systemic MSC injections significantly improve the pace and degree of nerve regeneration after nerve injury and hindlimb transplantation. PMID:27510321

  8. Hindlimb motion during steady flight of the lesser dog-faced fruit bat, Cynopterus brachyotis.

    PubMed

    Cheney, Jorn A; Ton, Daniel; Konow, Nicolai; Riskin, Daniel K; Breuer, Kenneth S; Swartz, Sharon M

    2014-01-01

    In bats, the wing membrane is anchored not only to the body and forelimb, but also to the hindlimb. This attachment configuration gives bats the potential to modulate wing shape by moving the hindlimb, such as by joint movement at the hip or knee. Such movements could modulate lift, drag, or the pitching moment. In this study we address: 1) how the ankle translates through space during the wingbeat cycle; 2) whether amplitude of ankle motion is dependent upon flight speed; 3) how tension in the wing membrane pulls the ankle; and 4) whether wing membrane tension is responsible for driving ankle motion. We flew five individuals of the lesser dog-faced fruit bat, Cynopterus brachyotis (Family: Pteropodidae), in a wind tunnel and documented kinematics of the forelimb, hip, ankle, and trailing edge of the wing membrane. Based on kinematic analysis of hindlimb and forelimb movements, we found that: 1) during downstroke, the ankle moved ventrally and during upstroke the ankle moved dorsally; 2) there was considerable variation in amplitude of ankle motion, but amplitude did not correlate significantly with flight speed; 3) during downstroke, tension generated by the wing membrane acted to pull the ankle dorsally, and during upstroke, the wing membrane pulled laterally when taut and dorsally when relatively slack; and 4) wing membrane tension generally opposed dorsoventral ankle motion. We conclude that during forward flight in C. brachyotis, wing membrane tension does not power hindlimb motion; instead, we propose that hindlimb movements arise from muscle activity and/or inertial effects.

  9. Medial prefrontal cortex acetylcholine injection-induced hypotension: the role of hindlimb vasodilation

    NASA Technical Reports Server (NTRS)

    Crippa, G. E.; Lewis, S. J.; Johnson, A. K.; Correa, F. M.

    2000-01-01

    The injection of acetylcholine (ACh) into the cingulate region of the medial prefrontal cortex (MPFC) causes a marked fall in arterial blood pressure which is not accompanied by changes in heart rate. The purpose of the present study was to investigate the hemodynamic basis for this stimulus-induced hypotension in Sprague-Dawley rats. The study was designed to determine whether a change in the vascular resistance of hindlimb, renal or mesenteric vascular beds contributes to the fall in arterial pressure in response to ACh injection into the cingulate cortex. Miniature pulsed-Doppler flow probes were used to measure changes in regional blood flow and vascular resistance. The results indicated that the hypotensive response was largely due to a consistent and marked vasodilation in the hindlimb vascular bed. On this basis, an additional experiment was then undertaken to determine the mechanisms that contribute to hindlimb vasodilation. The effect of interrupting the autonomic innervation of one leg on the hindlimb vasodilator response was tested. Unilateral transection of the lumbar sympathetic chain attenuated the cingulate ACh-induced vasodilation in the ipsilateral, but not in the contralateral hindlimb. These results suggest that the hypotensive response to cingulate cortex-ACh injection is caused by skeletal muscle vasodilation mediated by a sympathetic chain-related vasodilator system.

  10. Mesenchymal Stem Cells Enhance Nerve Regeneration in a Rat Sciatic Nerve Repair and Hindlimb Transplant Model.

    PubMed

    Cooney, Damon S; Wimmers, Eric G; Ibrahim, Zuhaib; Grahammer, Johanna; Christensen, Joani M; Brat, Gabriel A; Wu, Lehao W; Sarhane, Karim A; Lopez, Joseph; Wallner, Christoph; Furtmüller, Georg J; Yuan, Nance; Pang, John; Sarkar, Kakali; Lee, W P Andrew; Brandacher, Gerald

    2016-01-01

    This study investigates the efficacy of local and intravenous mesenchymal stem cell (MSC) administration to augment neuroregeneration in both a sciatic nerve cut-and-repair and rat hindlimb transplant model. Bone marrow-derived MSCs were harvested and purified from Brown-Norway (BN) rats. Sciatic nerve transections and repairs were performed in three groups of Lewis (LEW) rats: negative controls (n = 4), local MSCs (epineural) injection (n = 4), and systemic MSCs (intravenous) injection (n = 4). Syngeneic (LEW-LEW) (n = 4) and allogeneic (BN-LEW) (n = 4) hindlimb transplants were performed and assessed for neuroregeneration after local or systemic MSC treatment. Rats undergoing sciatic nerve cut-and-repair and treated with either local or systemic injection of MSCs had significant improvement in the speed of recovery of compound muscle action potential amplitudes and axon counts when compared with negative controls. Similarly, rats undergoing allogeneic hindlimb transplants treated with local injection of MSCs exhibited significantly increased axon counts. Similarly, systemic MSC treatment resulted in improved nerve regeneration following allogeneic hindlimb transplants. Systemic administration had a more pronounced effect on electromotor recovery while local injection was more effective at increasing fiber counts, suggesting different targets of action. Local and systemic MSC injections significantly improve the pace and degree of nerve regeneration after nerve injury and hindlimb transplantation. PMID:27510321

  11. The dynamic effect of muscle activation on knee stiffness.

    PubMed

    Ludvig, Daniel; Perreault, Eric J

    2014-01-01

    Adapting limb mechanics in a task and environment dependent manner is one component of human motor control. Joint mechanics have been extensively studied under static postural conditions, but less so under time-varying movement conditions. The limited studies that have investigated joint mechanics during movement, have found a drop in joint stiffness during movement, however the source of this decrease in stiffness remains unknown. Here in this paper we investigate whether time-varying muscle activation, which occurs during volitional movement, can lead to the drop in stiffness seen during movement. We found that under time-varying isometric conditions stiffness dropped when subjects transitioned from extension to flexion and vice-versa, a phenomenon that could not be explained by simply superimposing extension and flexion contractions. These findings suggest that dynamics of muscle activation may be responsible for the complex pattern of stiffness changes seen during simple movements. Furthermore, these results imply that EMG-based estimates of stiffness, which work well for steady-state postural conditions, will need to be augmented to account for the highly non-linear relationship between muscle activation and stiffness before they can also be used to estimate stiffness during dynamic contractions.

  12. Functional coordination of muscles underlying changes in behavioural dynamics.

    PubMed

    Vernooij, Carlijn A; Rao, Guillaume; Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor K; Temprado, Jean-Jacques

    2016-01-01

    The dynamical systems approach addresses Bernstein's degrees of freedom problem by assuming that the neuro-musculo-skeletal system transiently assembles and dismantles its components into functional units (or synergies) to meet task demands. Strikingly, little is known from a dynamical point of view about the functioning of the muscular sub-system in this process. To investigate the interaction between the dynamical organisation at muscular and behavioural levels, we searched for specific signatures of a phase transition in muscular coordination when a transition is displayed at the behavioural level. Our results provide evidence that, during Fitts' task when behaviour switches to a different dynamical regime, muscular activation displays typical signatures of a phase transition; a reorganisation in muscular coordination patterns accompanied by a peak in the variability of muscle activation. This suggests that consistent changes occur in coordination processes across the different levels of description (i.e., behaviour and muscles). Specifically, in Fitts' task, target size acts as a control parameter that induces a destabilisation and a reorganisation of coordination patterns at different levels of the neuro-musculo-skeletal system. PMID:27282349

  13. Functional coordination of muscles underlying changes in behavioural dynamics

    PubMed Central

    Vernooij, Carlijn A.; Rao, Guillaume; Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor K.; Temprado, Jean-Jacques

    2016-01-01

    The dynamical systems approach addresses Bernstein’s degrees of freedom problem by assuming that the neuro-musculo-skeletal system transiently assembles and dismantles its components into functional units (or synergies) to meet task demands. Strikingly, little is known from a dynamical point of view about the functioning of the muscular sub-system in this process. To investigate the interaction between the dynamical organisation at muscular and behavioural levels, we searched for specific signatures of a phase transition in muscular coordination when a transition is displayed at the behavioural level. Our results provide evidence that, during Fitts’ task when behaviour switches to a different dynamical regime, muscular activation displays typical signatures of a phase transition; a reorganisation in muscular coordination patterns accompanied by a peak in the variability of muscle activation. This suggests that consistent changes occur in coordination processes across the different levels of description (i.e., behaviour and muscles). Specifically, in Fitts’ task, target size acts as a control parameter that induces a destabilisation and a reorganisation of coordination patterns at different levels of the neuro-musculo-skeletal system. PMID:27282349

  14. Murine Model of Hindlimb Ischemia

    PubMed Central

    Niiyama, Hiroshi; Huang, Ngan F.; Rollins, Mark D.; Cooke, John P.

    2009-01-01

    In the United States, peripheral arterial disease (PAD) affects about 10 million individuals, and is also prevalent worldwide. Medical therapies for symptomatic relief are limited. Surgical or endovascular interventions are useful for some individuals, but long-term results are often disappointing. As a result, there is a need for developing new therapies to treat PAD. The murine hindlimb ischemia preparation is a model of PAD, and is useful for testing new therapies. When compared to other models of tissue ischemia such as coronary or cerebral artery ligation, femoral artery ligation provides for a simpler model of ischemic tissue. Other advantages of this model are the ease of access to the femoral artery and low mortality rate. In this video, we demonstrate the methodology for the murine model of unilateral hindimb ischemia. The specific materials and procedures for creating and evaluating the model will be described, including the assessment of limb perfusion by laser Doppler imaging. This protocol can also be utilized for the transplantation and non-invasive tracking of cells, which is demonstrated by Huang et al.1. PMID:19229179

  15. Feasible Muscle Activation Ranges Based on Inverse Dynamics Analyses of Human Walking

    PubMed Central

    Simpson, Cole S.; Sohn, M. Hongchul; Allen, Jessica L.; Ting, Lena H.

    2015-01-01

    Although it is possible to produce the same movement using an infinite number of different muscle activation patterns owing to musculoskeletal redundancy, the degree to which observed variations in muscle activity can deviate from optimal solutions computed from biomechanical models is not known. Here, we examined the range of biomechanically permitted activation levels in individual muscles during human walking using a detailed musculoskeletal model and experimentally-measured kinetics and kinematics. Feasible muscle activation ranges define the minimum and maximum possible level of each muscle’s activation that satisfy inverse dynamics joint torques assuming that all other muscles can vary their activation as needed. During walking, 73% of the muscles had feasible muscle activation ranges that were greater than 95% of the total muscle activation range over more than 95% of the gait cycle, indicating that, individually, most muscles could be fully active or fully inactive while still satisfying inverse dynamics joint torques. Moreover, the shapes of the feasible muscle activation ranges did not resemble previously-reported muscle activation patterns nor optimal solutions, i.e. static optimization and computed muscle control, that are based on the same biomechanical constraints. Our results demonstrate that joint torque requirements from standard inverse dynamics calculations are insufficient to define the activation of individual muscles during walking in healthy individuals. Identifying feasible muscle activation ranges may be an effective way to evaluate the impact of additional biomechanical and/or neural constraints on possible versus actual muscle activity in both normal and impaired movements. PMID:26300401

  16. Dynamic mechanical assessment of muscle hyperalgesia in humans: The dynamic algometer

    PubMed Central

    Finocchietti, Sara; Graven-Nielsen, Thomas; Arendt-Nielsen, Lars

    2015-01-01

    BACKGROUND: Musculoskeletal pain is often associated with a nonhomogeneous distribution of mechanical hyperalgesia. Consequently, new methods able to detect this distribution are needed. OBJECTIVE: To develop and test a new method for assessing muscle hyperalgesia with high temporal and spatial resolution that provides complementary information compared with information obtained by traditional static pressure algometry. METHODS: The dynamic pressure algometer was tested bilaterally on the tibialis anterior muscle in 15 healthy subjects and compared with static pressure algometry. The device consisted of a wheel that was rolled over the muscle tissue with a fixed velocity and different predefined forces. The pain threshold force was determined and pain intensity to a fixed-force stimulation was continuously rated on a visual analogue scale while the wheel was rolling over the muscle. The pressure pain sensitivity was evaluated before, during, and after muscle pain and hyperalgesia induced unilaterally by either injection of hypertonic saline (0.5 mL, 6%) into the tibialis anterior or eccentric exercise evoking delayed-onset muscle soreness (DOMS). RESULTS: The intraclass correlation coefficient was >0.88 for the dynamic thresholds; thus, the method was reliable. Compared with baseline, both techniques detected hyperalgesia at the saline injection site and during DOMS (P<0.05). The dynamic algometer also detected the widespread, patchy distribution of sensitive loci during DOMS, which was difficult to evaluate using static pressure algometry. DISCUSSION AND CONCLUSION: The present study showed that dynamic pressure algometry is a reliable tool for evaluating muscle hyperalgesia (threshold and pain rating) with high temporal and spatial resolution. It can be applied as a simple clinical bed-side test and as a quantitative tool in pharmacological profiling studies. PMID:25664539

  17. Dynamics and Thermodynamics of Artificial Muscles Based on Nematic Gels

    NASA Astrophysics Data System (ADS)

    Hébert, M.; Kant, R.; de Gennes, P.-G.

    1997-07-01

    A scheme based on nemato-mechanical conversion has been proposed for potential artificial muscle applications (de Gennes P.-G., Hébert M. and Kant R., to appear in Macromol. Symp. (1996)). As the temperature in a nematic gel is reduced through the transition temperature, strong uniaxial deformation is encountered. We briefly expose the dynamics of contraction/elongation in this system. Work and dissipative losses are calculated for an operating cycle to get an approximative expression of the ratio work/losses, which can then be compared with real muscular efficiencies.

  18. Prediction of Muscle Performance During Dynamic Repetitive Exercise

    NASA Technical Reports Server (NTRS)

    Byerly, D. L.; Byerly, K. A.; Sognier, M. A.; Squires, W. G.

    2002-01-01

    A method for predicting human muscle performance was developed. Eight test subjects performed a repetitive dynamic exercise to failure using a Lordex spinal machine. Electromyography (EMG) data was collected from the erector spinae. Evaluation of the EMG data using a 5th order Autoregressive (AR) model and statistical regression analysis revealed that an AR parameter, the mean average magnitude of AR poles, can predict performance to failure as early as the second repetition of the exercise. Potential applications to the space program include evaluating on-orbit countermeasure effectiveness, maximizing post-flight recovery, and future real-time monitoring capability during Extravehicular Activity.

  19. Muscle Oxygen Dynamics During Cycling Exercise in Angina Pectoris Patients.

    PubMed

    Takagi, Shun; Murase, Norio; Kime, Ryotaro; Niwayama, Masatsugu; Osada, Takuya; Katsumura, Toshihito

    2016-01-01

    Muscle O2 dynamics during ramp cycling exercise were compared between angina pectoris patients (AP; n = 7, age: 73 ± 6 years) after coronary artery bypass grafting and age-, height-, and body weight-matched elderly control subjects (CON; n = 7, age: 74 ± 8 years). Muscle O2 saturation (SmO2) and relative change in deoxygenated (∆deoxy-Hb) and total hemoglobin concentration (∆total-Hb) were measured continuously during exercise in the vastus lateralis (VL) by near infrared spatial resolved spectroscopy. Pulmonary O2 uptake (VO2) was also monitored throughout exercise to determine peak VO2. In AP, SmO2 was significantly higher, and ∆deoxy-Hb was significantly lower during exercise, compared to CON. In all subjects, ∆SmO2 (values at peak exercise minus values at resting) was negatively correlated to peak VO2 (r = -0.52, p < 0.05), and ∆deoxy-Hb at peak exercise tended to be negatively associated with peak VO2 (r = 0.48, p = 0.07). Blunted skeletal muscle deoxygenation response was observed in AP patients, which may be related to lower aerobic capacity in AP patients. PMID:27526156

  20. Regulatory and Catalytic Domain Dynamics of Smooth Muscle Myosin Filaments†

    PubMed Central

    Li, Hui-Chun; Song, Likai; Salzameda, Bridget; Cremo, Christine R.; Fajer, Piotr G.

    2016-01-01

    Domain dynamics of the chicken gizzard smooth muscle myosin catalytic domain (heavy chain Cys-717) and regulatory domain (regulatory light chain Cys-108) were determined in the absence of nucleotides using saturation-transfer electron paramagnetic resonance. In unphosphorylated synthetic filaments, the effective rotational correlation times, τr, were 24 ± 6 μs and 441 ± 79 μs for the catalytic and regulatory domains, respectively. The corresponding amplitudes of motion were 42 ± 4° and 24 ± 9° as determined from steady-state phosphorescence anisotropy. These results suggest that the two domains have independent mobility due to a hinge between the two domains. Although a similar hinge was observed for skeletal myosin (Adhikari and Fajer (1997) Proc. Natl. Acad. Sci. U.S.A. 94, 9643–9647. Brown et al. (2001) Biochemistry 40, 8283–8291), the latter displayed higher regulatory domain mobility, τr = 40 ± 3 μs, suggesting a smooth muscle specific mechanism of constraining regulatory domain dynamics. In the myosin monomers the correlation times for both domains were the same (~4 μs) for both smooth and skeletal myosin, suggesting that the motional difference between the two isoforms in the filaments was not due to intrinsic variation of hinge stiffness. Heavy chain/regulatory light chain chimeras of smooth and skeletal myosin pinpointed the origin of the restriction to the heavy chain and established correlation between the regulatory domain dynamics with the ability of myosin to switch off but not to switch on the ATPase and the actin sliding velocity. Phosphorylation of smooth muscle myosin filaments caused a small increase in the amplitude of motion of the regulatory domain (from 24 ± 4° to 36 ± 7°) but did not significantly affect the rotational correlation time of the regulatory domain (441 to 408 μs) or the catalytic domain (24 to 17 μs). These data are not consistent with a stable interaction between the two catalytic domains in

  1. A metabolic cage for the hindlimb suspended rat

    NASA Technical Reports Server (NTRS)

    Evans, J.; Mulenburg, G. M.; Harper, J. S.; Skundberg, T. L.; Navidi, M.; Arnaud, S. B.

    1994-01-01

    Hindlimb suspension has been successfully used to simulate the effects of microgravity in rats. The cage and suspension system developed by E. R. Holton is designed to produce a headward shift of fluid and unload the hindlimbs in rodents, causing changes in bone and muscle similar to those in animals and humans exposed to spaceflight. While the Holton suspension system simulates many of the conditions observed in the spaceflight animal, it does not provide for the collection of urine and feces needed to monitor some metabolic activities. As a result, only limited information has been gathered on the nutritional status, and the gastrointestinal and renal function of animals using that model. Although commercial metabolic cages are available, they are usually cylindrical and require a centrally located suspension system and thus, do not readily permit movement of the rats. The limited floor space of commercial cages may affect comparisons with studies using the Holton model which has more than twice the living space of most commercially available cages. To take advantage of the extra living space and extensive data base that has been developed with the Holton model, Holton's cage was modified to make urine and fecal collections possible.

  2. Precocial hindlimbs and altricial forelimbs: partitioning ontogenetic strategies in mallards (Anas platyrhynchos).

    PubMed

    Dial, Terry R; Carrier, David R

    2012-11-01

    Precocial development, in which juveniles are relatively mature at hatching or birth, is more common among vertebrates than altricial development, and is likely to be the basal condition. Altricial development characterizes many birds and mammals and is generally viewed as an alternate strategy, promoting fast growth rates, short developmental periods and relatively poor locomotor performance prior to attaining adult size. Many aquatic birds such as Anseriformes (ducks, geese and swans), Charadriformes (gulls and terns) and Gruiformes (rails) undergo distinctive developmental trajectories, in that hatchlings are able to run and swim the day they hatch, yet they do not begin to fly until fully grown. We hypothesized that there should be tradeoffs in apportioning bone and muscle mass to the hindlimb and forelimb that could account for these patterns in locomotor behavior within the mallard (Anas platyrhynchos). Growth of the musculoskeletal system in the forelimbs and hindlimbs was measured and compared with maximal aquatic and terrestrial sprint speeds and aerial descent rates throughout the 2-month-long mallard ontogenetic period. At 30 days post hatching, when body mass is 50% of adult values, hindlimb muscle mass averages 90% and forelimb muscle mass averages 10% of adult values; similarly, bone growth (length and width) in the hindlimbs and forelimbs averages 90 and 60% of adult values, respectively. The attainment of mallard locomotor performance parallels the morphological maturation of forelimb and hindlimb morphometrics - hindlimb performance initiates just after hatching at a relatively high level (~50% adult values) and gradually improves throughout the first month of development, while forelimb performance is relatively non-existent at hatching (~10% adult values), experiencing delayed and dramatic improvement in function, and maturing at the time of fledging. This divergence in ontogenetic strategy between locomotor modules could allow developing

  3. Hindlimb myology of the monk parakeet (Aves, Psittaciformes).

    PubMed

    Carril, Julieta; Mosto, María C; Picasso, Mariana B J; Tambussi, Claudia P

    2014-07-01

    We studied the hindlimb myology of the monk parakeet (Myiopsitta monachus). Like all parrots, it has zygodactyl feet enabling perching, climbing, hanging, moving easily among trees, and handling food. Muscles were described and weighed, and physiological cross-sectional area (PCSA) of four flexors and one extensor was calculated. In comparison to other muscles, the M. tibialis cranialis and the M. fibularis brevis show increased development and high PCSA values, and therefore, large potential force production. Also, a large proportion of muscle mass was involved in flexing the digits. We hypothesize that these muscle traits are associated with the arboreal locomotion and food manipulation habits. In the monk parakeet, the M. extensor digitorum longus sends a branch to the hallux, and the connection between the M. flexor digitorum longus and the M. flexor hallucis longus is type I (Gadow's classification). We reaffirm the presence of the M. ambiens as a plesiomorphic condition that disappears in most members of the order. Among Psittaciformes, the M. fibularis brevis is stronger and the M. fibularis weaker in arboreal species than in basal terrestrial ones (e.g., Strigops).

  4. Noninvasive Tracking of Quiescent and Activated Muscle Stem Cell (MuSC) Engraftment Dynamics In Vivo.

    PubMed

    Ho, Andrew T V; Blau, Helen M

    2016-01-01

    Muscle stem cells play a central role in muscle regeneration. Most studies in the field of muscle regeneration focus on the unraveling of muscle stem cell biology to devise strategies for treating failing muscles as seen in aging and muscle-related diseases. However, the common method used in assessing stem cell function in vivo is laborious, as it involves time-consuming immunohistological analyses by microscopy on serial cryo-sections of the muscle post stem cell transplantation. Here we describe an alternative method, which adapts the bioluminescence imaging (BLI) technique to allow noninvasive tracking of engrafted stem-cell function in vivo in real-time. This assay system enables longitudinal studies in the same mice over time and reveals parameters, not feasible by traditional analysis, such as the magnitude and dynamics of engrafted muscle stem cell expansion in vivo in response to a particular drug treatment or muscle injury. PMID:27492173

  5. The effect of kinesiotape on dynamic balance following muscle fatigue in individuals with chronic ankle instability.

    PubMed

    Kodesh, Einat; Dar, Gali

    2015-01-01

    This study aimed to evaluate the effect of kinesiotape (KT) on dynamic stability following ankle muscle fatigue among individuals with chronic ankle instability (CAI). Twenty participants with CAI participated in the study. Participants were tested under three conditions: KT, non-elastic tape, and no tape pre- and post-fatigue of the ankle muscles. Ankle muscles fatigue was induced using an isokinetic apparatus, activity of the fibularis muscle was recorded using one-channel vibromyography (VMG), and dynamic balance and neuromuscular control were assessed using the Y-Balance Test. Following fatigue exercises, the VMG signal significantly decreased in all groups (p < 0.01), without differences between groups. No significant difference in dynamic balance test scores was found between the pre- and post-fatigue condition for each group and between groups. Our results demonstrate that KT had no significant effects on dynamic balance and muscle activity following ankle muscle fatigue among individuals with CAI. PMID:26279271

  6. Endothelin-1 induces endothelial barrier failure in the cat hindlimb.

    PubMed

    Porter, L P; McNamee, J E; Wolf, M B

    1999-02-01

    Our purpose was to see whether endothelin- (ET) 1 could produce a change in the endothelial membrane barrier to protein in skeletal muscle. Previous studies in other tissues have suggested that ET-1 affects this barrier, but the measurement methods used could not exclude vascular protein extravasation due to microvascular pressure changes or the effects of changes in perfused capillary surface area. We measured the protein sieving coefficient, a specific measure of the permeability of the membrane to protein, in the isolated, perfused cat hindlimb preparation. The integral-mass balance method determined this coefficient from the changes in hematocrit and plasma protein concentration induced by a period of transvascular fluid filtration. The data clearly indicate that ET-1 produces a dose (1-20 nM) dependent increase in permeability indicative of barrier dysfunction. Hence, elevated ET levels may contribute to the perivascular edema, hemoconcentration, and impaired tissue perfusion found in systemic inflammatory response syndromes and related diseases. PMID:10030797

  7. A nonlinear model of the phasic dynamics of muscle activation

    NASA Technical Reports Server (NTRS)

    Hannaford, Blake

    1990-01-01

    A phasic excitation-activation (PEXA) model is presented of the process of motoneuron excitation and the resultant activation and force development of a motor unit. The model input is an amount of depolarizing current (as when injected with an intracellular electrode), and the model output is muscle force. The model includes dynamics and nonlinearities similar to phenomena discovered experimentally by others: the firing rate response of motoneurons to steps of depolarizing current and the catch-like enhancement of force produced by overlapping motor neuron action potentials. The parameter values used in this model are derived from experimentally measured data and are expressed in physical units. Model predictions extend to published data beyond those used in generating the model parameter values.

  8. Influence of Androgen Receptor in Vascular Cells on Reperfusion following Hindlimb Ischaemia

    PubMed Central

    Hadoke, Patrick W. F.; Takov, Kaloyan; Korczak, Agnieszka; Denvir, Martin A.; Smith, Lee B.

    2016-01-01

    Aims Studies in global androgen receptor knockout (G-ARKO) and orchidectomised mice suggest that androgen accelerates reperfusion of the ischaemic hindlimb by stimulating angiogenesis. This investigation used novel, vascular cell-specific ARKO mice to address the hypothesis that the impaired hindlimb reperfusion in G-ARKO mice was due to loss of AR from cells in the vascular wall. Methods and Results Mice with selective deletion of AR (ARKO) from vascular smooth muscle cells (SM-ARKO), endothelial cells (VE-ARKO), or both (SM/VE-ARKO) were compared with wild type (WT) controls. Hindlimb ischaemia was induced in these mice by ligation and removal of the femoral artery. Post-operative reperfusion was reduced in SM-ARKO and SM/VE-ARKO mice. Immunohistochemistry indicated that this was accompanied by a reduced density of smooth muscle actin-positive vessels but no change in the density of isolectin B4-positive vessels in the gastrocnemius muscle. Deletion of AR from the endothelium (VE-ARKO) did not alter post-operative reperfusion or vessel density. In an ex vivo (aortic ring culture) model of angiogenesis, AR was not detected in vascular outgrowths and angiogenesis was not altered by vascular ARKO or by exposure to dihydrotestosterone (DHT 10−10–10-7M; 6 days). Conclusion These results suggest that loss of AR from vascular smooth muscle, but not from the endothelium, contributes to impaired reperfusion in the ischaemic hindlimb of G-ARKO. Impaired reperfusion was associated with reduced collateral formation rather than reduced angiogenesis. PMID:27159530

  9. Hindlimb unloading rodent model: technical aspects

    NASA Technical Reports Server (NTRS)

    Morey-Holton, Emily R.; Globus, Ruth K.

    2002-01-01

    Since its inception at the National Aeronautics and Space Administration (NASA) Ames Research Center in the mid-1970s, many laboratories around the world have used the rat hindlimb unloading model to simulate weightlessness and to study various aspects of musculoskeletal loading. In this model, the hindlimbs of rodents are elevated to produce a 30 degrees head-down tilt, which results in a cephalad fluid shift and avoids weightbearing by the hindquarters. Although several reviews have described scientific results obtained with this model, this is the first review to focus on the technical aspects of hindlimb unloading. This review includes a history of the technique, a brief comparison with spaceflight data, technical details, extension of the model to mice, and other important technical considerations (e.g., housing, room temperature, unloading angle, the potential need for multiple control groups, age, body weight, the use of the forelimb tissues as internal controls, and when to remove animals from experiments). This paper is intended as a reference for researchers, reviewers of manuscripts, and institutional animal care and use committees. Over 800 references, related to the hindlimb unloading model, can be accessed via the electronic version of this article.

  10. Vasoconstrictors alter oxygen, lactate, and glycerol metabolism in the perfused hindlimb of a rat kangaroo.

    PubMed

    Ye, J M; Edwards, S J; Rose, R W; Rattigan, S; Clark, M G; Colquhoun, E Q

    1995-05-01

    The Tasmanian bettong (Bettongia gaimardi) is a small marsupial rat kangaroo without detectable brown adipose tissue (BAT). The hindlimb was perfused with constant flow at 25 degrees C after cannulation under anesthesia of the femoral artery and vein to one hindlimb. Norepinephrine (NE, 25 nM-2.5 microM) and vasopressin (VP, 10 nM-0.1 microM) each increased perfusion pressure, oxygen consumption (VO2), and lactate and glycerol efflux of the perfused hindlimb. NE-mediated increases in VO2 and the efflux of lactate and glycerol were unaffected by propranolol (10 microM) but were completely blocked by the further addition of phentolamine (10 microM). In contrast, serotonin (5-HT; 0.1-2.5 microM) inhibited VO2 and inhibited lactate efflux. The changes induced by NE, VP, and 5-HT were all rapidly reversed by nitroprusside. These results suggest that resting thermogenesis in bettong hindlimb can be differentially controlled by the vasculature, which may also contribute to the induced VO2. This vascular control of skeletal muscle VO2 appears widespread in homeotherm evolution.

  11. Forms of forward quadrupedal locomotion. II. A comparison of posture, hindlimb kinematics, and motor patterns for upslope and level walking.

    PubMed

    Carlson-Kuhta, P; Trank, T V; Smith, J L

    1998-04-01

    To gain insight into the neural mechanisms controlling different forms of quadrupedal walking of normal cats, data on postural orientation, hindlimb kinematics, and motor patterns of selected hindlimb muscles were assessed for four grades of upslope walking, from 25 to 100% (45 degrees incline), and compared with similar data for level treadmill walking (0.6 m/s). Kinematic data for the hip, knee, ankle, and metatarsophalangeal joints were obtained from digitizing ciné film that was synchronized with electromyographic (EMG) records from 13 different hindlimb muscles. Cycle periods, the structure of the step cycle, and paw-contact sequences were similar at all grades and typical of lateral-sequence walking. Also, a few half-bound and transverse gallop steps were assessed from trials at the 100% grade; these steps had shorter cycle periods than the walking steps and less of the cycle (68 vs. 56%) was devoted to stance. Each cat assumed a crouched posture at the steeper grades of upslope walking and stride length decreased, whereas the overall position of the stride shifted caudally with respect to the hip joint. At the steeper grades, the range and duration of swing-related flexion increased at all joints, the stance-phase yield was absent at the knee and ankle joints, and the range of stance-phase extension at knee and ankle joints increased. Patterns of muscle activity for upslope and level walking were similar with some notable exceptions. At the steeper grades, the EMG activity of muscles with swing-related activity, such as the digit flexor muscle, the flexor digitorum longus (FDL), and the knee flexor muscle, the semitendinosus (ST), was prolonged and continued well into midswing. The EMG activity of stance-related muscles also increased in amplitude with grade, and three muscles not active during the stance phase of level walking had stance activity that increased in amplitude and duration at the steepest grades; these muscles were the ST, FDL, and extensor

  12. In-vivo measurement of muscle tension: dynamic properties of the MC sensor during isometric muscle contraction.

    PubMed

    Đorđević, Srđan; Tomažič, Sašo; Narici, Marco; Pišot, Rado; Meglič, Andrej

    2014-01-01

    Skeletal muscle is the largest tissue structure in our body and plays an essential role for producing motion through integrated action with bones, tendons, ligaments and joints, for stabilizing body position, for generation of heat through cell respiration and for blood glucose disposal. A key function of skeletal muscle is force generation. Non-invasive and selective measurement of muscle contraction force in the field and in clinical settings has always been challenging. The aim of our work has been to develop a sensor that can overcome these difficulties and therefore enable measurement of muscle force during different contraction conditions. In this study, we tested the mechanical properties of a "Muscle Contraction" (MC) sensor during isometric muscle contraction in different length/tension conditions. The MC sensor is attached so that it indents the skin overlying a muscle group and detects varying degrees of tension during muscular contraction. We compared MC sensor readings over the biceps brachii (BB) muscle to dynamometric measurements of force of elbow flexion, together with recordings of surface EMG signal of BB during isometric contractions at 15° and 90° of elbow flexion. Statistical correlation between MC signal and force was very high at 15° (r = 0.976) and 90° (r = 0.966) across the complete time domain. Normalized SD or σN = σ/max(FMC) was used as a measure of linearity of MC signal and elbow flexion force in dynamic conditions. The average was 8.24% for an elbow angle of 90° and 10.01% for an elbow of angle 15°, which indicates high linearity and good dynamic properties of MC sensor signal when compared to elbow flexion force. The next step of testing MC sensor potential will be to measure tension of muscle-tendon complex in conditions when length and tension change simultaneously during human motion.

  13. A 3D analysis of fore- and hindlimb motion during overground and ladder walking: comparison of control and unloaded rats.

    PubMed

    Canu, Marie-Hélène; Garnier, Cyril

    2009-07-01

    During locomotion, muscles are controlled by a network of neurones located in the spinal cord and by supraspinal structures. Alterations in that neuromuscular system have a functional impact, in particular on locomotion. The hindlimb unloading (HU) model in rat has been commonly used to generate disuse since it suppresses the hindlimb loading and limits movements. In consequence, it induces plastic mechanisms in the muscle, the spinal cord and the sensorimotor cortex. The aim of this study was to assess the locomotion in HU rats in two conditions: (1) on a runway and (2) in a challenging situation involving the participation of supraspinal structures (ladder walking). For that purpose, the motor pattern has been investigated by means of 3D motion analysis of the right fore- and hindlimbs as well as electromyographic recording of the soleus and tibialis anterior muscles. The 3D motion results show that HU induces a support-dependent alteration of the kinematics: increased duration of step, stance and swing; increased ankle flexion during stance and hyperextension at toe-off; lower protraction during swing. The electromyographic results show that whatever the support, the flexor and extensor burst duration was longer in HU rats. In addition, results show that ladder exacerbates some effects of HU. As ladder walking is a situation which requires precision, it is suggested that the control of hindlimb movement by supraspinal structures is affected in HU rats. PMID:19393236

  14. Hindlimb Motion during Steady Flight of the Lesser Dog-Faced Fruit Bat, Cynopterus brachyotis

    PubMed Central

    Cheney, Jorn A.; Ton, Daniel; Konow, Nicolai; Riskin, Daniel K.; Breuer, Kenneth S.; Swartz, Sharon M.

    2014-01-01

    In bats, the wing membrane is anchored not only to the body and forelimb, but also to the hindlimb. This attachment configuration gives bats the potential to modulate wing shape by moving the hindlimb, such as by joint movement at the hip or knee. Such movements could modulate lift, drag, or the pitching moment. In this study we address: 1) how the ankle translates through space during the wingbeat cycle; 2) whether amplitude of ankle motion is dependent upon flight speed; 3) how tension in the wing membrane pulls the ankle; and 4) whether wing membrane tension is responsible for driving ankle motion. We flew five individuals of the lesser dog-faced fruit bat, Cynopterus brachyotis (Family: Pteropodidae), in a wind tunnel and documented kinematics of the forelimb, hip, ankle, and trailing edge of the wing membrane. Based on kinematic analysis of hindlimb and forelimb movements, we found that: 1) during downstroke, the ankle moved ventrally and during upstroke the ankle moved dorsally; 2) there was considerable variation in amplitude of ankle motion, but amplitude did not correlate significantly with flight speed; 3) during downstroke, tension generated by the wing membrane acted to pull the ankle dorsally, and during upstroke, the wing membrane pulled laterally when taut and dorsally when relatively slack; and 4) wing membrane tension generally opposed dorsoventral ankle motion. We conclude that during forward flight in C. brachyotis, wing membrane tension does not power hindlimb motion; instead, we propose that hindlimb movements arise from muscle activity and/or inertial effects. PMID:24858194

  15. An Accurate and Dynamic Computer Graphics Muscle Model

    NASA Technical Reports Server (NTRS)

    Levine, David Asher

    1997-01-01

    A computer based musculo-skeletal model was developed at the University in the departments of Mechanical and Biomedical Engineering. This model accurately represents human shoulder kinematics. The result of this model is the graphical display of bones moving through an appropriate range of motion based on inputs of EMGs and external forces. The need existed to incorporate a geometric muscle model in the larger musculo-skeletal model. Previous muscle models did not accurately represent muscle geometries, nor did they account for the kinematics of tendons. This thesis covers the creation of a new muscle model for use in the above musculo-skeletal model. This muscle model was based on anatomical data from the Visible Human Project (VHP) cadaver study. Two-dimensional digital images from the VHP were analyzed and reconstructed to recreate the three-dimensional muscle geometries. The recreated geometries were smoothed, reduced, and sliced to form data files defining the surfaces of each muscle. The muscle modeling function opened these files during run-time and recreated the muscle surface. The modeling function applied constant volume limitations to the muscle and constant geometry limitations to the tendons.

  16. Mechanomyographic amplitude and frequency responses during dynamic muscle actions: a comprehensive review

    PubMed Central

    Beck, Travis W; Housh, Terry J; Cramer, Joel T; Weir, Joseph P; Johnson, Glen O; Coburn, Jared W; Malek, Moh H; Mielke, Michelle

    2005-01-01

    The purpose of this review is to examine the literature that has investigated mechanomyographic (MMG) amplitude and frequency responses during dynamic muscle actions. To date, the majority of MMG research has focused on isometric muscle actions. Recent studies, however, have examined the MMG time and/or frequency domain responses during various types of dynamic activities, including dynamic constant external resistance (DCER) and isokinetic muscle actions, as well as cycle ergometry. Despite the potential influences of factors such as changes in muscle length and the thickness of the tissue between the muscle and the MMG sensor, there is convincing evidence that during dynamic muscle actions, the MMG signal provides valid information regarding muscle function. This argument is supported by consistencies in the MMG literature, such as the close relationship between MMG amplitude and power output and a linear increase in MMG amplitude with concentric torque production. There are still many issues, however, that have yet to be resolved, and the literature base for MMG during both dynamic and isometric muscle actions is far from complete. Thus, it is important to investigate the unique applications of MMG amplitude and frequency responses with different experimental designs/methodologies to continually reassess the uses/limitations of MMG. PMID:16364182

  17. Knockdown of Ephrin-A5 Expression by 40% Does not Affect Motor Axon Growth or Migration into the Chick Hindlimb

    PubMed Central

    Winning, Robert S.; Krull, Catherine E.

    2011-01-01

    Bidirectional signaling between Eph receptor tyrosine kinases and their cell-surface protein signals, the ephrins, comprises one mechanism for guiding motor axons to their proper targets. During projection of motor axons from the lateral motor column (LMC) motor neurons of the spinal cord to the hindlimb muscles in chick embryos, ephrin-A5 has been shown to be expressed in the LMC motor axons until they reach the base of the limb bud and initiate sorting into their presumptive dorsal and ventral nerve trunks, at which point expression is extinguished. We tested the hypothesis that this dynamic pattern of ephrin-A5 expression in LMC motor axons is important for the growth and guidance of the axons to, and into, the hindlimb by knocking down endogenous ephrin-A5 expression in the motor neurons and their axons. No perturbation of LMC motor axon projections was observed in response to this treatment, suggesting that ephrin-A5 is not needed for LMC motor axon growth or guidance. PMID:22272077

  18. Muscle-driven forward dynamic simulations for the study of normal and pathological gait

    PubMed Central

    Piazza, Stephen J

    2006-01-01

    There has been much recent interest in the use of muscle-actuated forward dynamic simulations to describe human locomotion. These models simulate movement through the integration of dynamic equations of motion and usually are driven by excitation inputs to muscles. Because motion is effected by individual muscle actuators, these simulations offer potential insights into the roles played by muscles in producing walking motions. Better knowledge of the actions of muscles should lead to clarification of the etiology of movement disorders and more effective treatments. This article reviews the use of such simulations to characterize musculoskeletal function and describe the actions of muscles during normal and pathological locomotion. The review concludes by identifying ways in which models must be improved if their potential for clinical utility is to be realized. PMID:16519796

  19. Plume Dynamics of Laser-Produced Swine Muscle Tissue Plasma.

    PubMed

    Camacho, Joaquin J; Diaz, Luis; Marin-Roldan, Alicia; Moncayo, Samuel; Caceres, Jorge O

    2016-07-01

    We report on the plume dynamics of the plasma induced by laser ablation of a swine skeletal muscle tissue sample in different vacuum conditions. Pulses from a transversely excited atmospheric CO2 laser were focused onto a target sample and the induced plasma was allowed to expand in different air pressures. The expansion features were studied using fast photography of the overall visible emission by using a gated intensified charged coupled device. Free expansion and plume splitting were observed at different pressure levels. The expansion of the plasma plume front was analyzed using various expansion models and the velocity of the plume front was estimated. The effect of the number of accumulated laser shots on the crater volume at different ambient air pressures and an elemental analysis of the sample were performed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (EDX) analysis. The surface morphology of the irradiated surface showed that increasing the pressure of the ambient gas decreased the ablated mass, or in other words it reduced significantly the laser-target coupling. PMID:27301327

  20. Effect of Hindlimb Unweighting on Tissue Blood Flow in the Rat

    NASA Technical Reports Server (NTRS)

    McDonald, K. S.; Delp, M. D.; Fitts, R. H.

    1992-01-01

    The purpose of this study was to characterize the distribution of blood flow in the rat during hindlimb unweighting (HU) and post-HU standing and exercise and examine whether the previously reported elevation in anaerobic metabolism observed with contractile activity in the atrophied soleus muscle was caused by a reduced hindlimb blood flow. After either 15 days of HU or cage control, blood flow was measured with radioactive microspheres during unweighting, normal standing, and running on a treadmill (15 m/min). In another group of control and experimental animals, blood flow was measured during preexercise (PE) treadmill standing and treadmill running (15 m/min). Soleus muscle blood flow was not different between groups during unweighting, PE standing, and running at 15 m/min. Chronic unweighting resulted in the tendency for greater blood flow to muscles composed of predominantly fast-twitch glycolytic fibers. With exercise, blood flow to visceral organs was reduced compared with PE values in the control rats, whereas flow to visceral organs in 15-day HU animals was unaltered by exercise. These higher flows to the viscera and to muscles composed of predominantly fast-twitch glycolytic fibers suggest an apparent reduction in the ability of the sympathetic nervous system to distribute cardiac output after chronic HU. In conclusion, because 15 days of HU did not affect blood flow to the soleus during exercise, the increased dependence of the atrophied soleus on anerobic energy production during contractile activity cannot be explained by a reduced muscle blood flow.

  1. Comparison of the Physiology of the Spaceflight and Hindlimb Suspended Rat

    NASA Technical Reports Server (NTRS)

    Grindeland, R. E.; Booth, F. W.

    1994-01-01

    The suspended rat has been used extensively as a simulation of the spaceflight animal. In suspension, hindlimbs are unloaded from the acceleration of gravity, much as they are in spaceflight. Comparisons of data from spaceflight (microgravity) and suspended (1G) rats have suggested that suspension my be an appropriate model, but no direct comparisons had been made between the spaceflight and suspended rat. Cosmos 2044 afforded the first opportunity to directly compare the effects of hindlimb suspension (HS) and spaceflight (SF) on a broad range of physiological and histological parameters. This paper reports on the comparison of skelton, skeletal muscle, heart, neural, pulmonary, kidney, liver, intestine, blood plasma, immune function, red blood cells, and endocrine and reproductive functions and systems.

  2. Axon Regeneration Can Facilitate or Suppress Hindlimb Function after Olfactory Ensheathing Glia Transplantation

    PubMed Central

    Takeoka, Aya; Jindrich, Devin L.; Muñoz-Quiles, Cintia; Zhong, Hui; van den Brand, Rubia; Pham, Daniel L.; Ziegler, Matthias D.; Ramón-Cueto, Almudena; Roy, Roland R.; Edgerton, V. Reggie

    2011-01-01

    Reports based primarily on anatomical evidence suggest that olfactory ensheathing glia (OEG) transplantation promotes axon regeneration across a complete spinal cord transection in adult rats. Based on functional, electrophysiological, and anatomical assessments, we found that OEG promoted axon regeneration across a complete spinal cord transection and that this regeneration altered motor responses over time. At 7 months after transection, 70% of OEG-treated rats showed motor-evoked potentials in hindlimb muscles after transcranial electric stimulation. Furthermore, a complete spinal cord retransection performed 8 months after injury demonstrated that this axon regeneration suppressed locomotor performance and decreased the hypersensitive hindlimb withdrawal response to mechanical stimulation. OEG transplantation alone promoted reorganization of lumbosacral locomotor networks and, when combined with long-term training, enhanced some stepping measures. These novel findings demonstrate that OEG promote regeneration of mature axons across a complete transection and reorganization of spinal circuitry, both of which contribute to sensorimotor function. PMID:21411671

  3. Rostro-Caudal Inhibition of Hindlimb Movements in the Spinal Cord of Mice

    PubMed Central

    Caggiano, Vittorio; Sur, Mirganka; Bizzi, Emilio

    2014-01-01

    Inhibitory neurons in the adult mammalian spinal cord are known to locally modulate afferent feedback - from muscle proprioceptors and from skin receptors - to pattern motor activity for locomotion and postural control. Here, using optogenetic tools, we explored how the same population of inhibitory interneurons globally affects hindlimb movements in the spinal cord of both anesthetized and freely moving mice. Activation of inhibitory interneurons up to the middle/lower spinal cord i.e. T8–T9, were able to completely and globally suppress all ipsilateral hindlimb movements. Furthermore, the same population of interneurons - which inhibited movements - did not significantly change the sensory and proprioceptive information from the affected limbs to the cortex. These results suggest a rostro-caudal organization of inhibition in the spinal cord motor output without modulation of ascending sensory pathways. PMID:24963653

  4. Properties of cat neck muscle spindles and their excitation by succinylcholine.

    PubMed

    Price, R F; Dutia, M B

    1987-01-01

    The sensitivity to sinusoidal stretching and small-amplitude vibration, and the variability of the resting discharge rate of de-efferented muscle spindles in the neck extensor muscle biventer cervicis (b.c.) of the cat have been studied. The effects of intra-arterial infusion of succinylcholine (SCh) on the response of the receptors to ramp stretches of the muscle were also determined. When activated by SCh, one group of afferents showed only a slow facilitation of their discharge rate, similar to that of spindle secondary sensory endings in hind-limb muscles. A second group of afferents developed a large dynamic response and a marked increase in their static discharge rate and were presumed to originate in "normal" b1b2 c spindles in the b.c. muscle. A third group of afferents developed only a marked increase in static discharge, without potentiation of the dynamic response, suggesting an origin in the b2c units of tandem spindles which are relatively common in the neck muscles. On the basis of their passive characteristics alone, afferents from b1b2c units could not be readily distinguished from those from b2c units. The characteristics of these receptors, and their differences from the well-studied hind-limb spindle afferents, are discussed.

  5. Muscle dynamics differences between legs in healthy adults.

    PubMed

    Flanagan, Eamonn P; Harrison, Andrew J

    2007-02-01

    Differences in muscle dynamics between the preferred and nonpreferred jumping legs of subjects in maximal, explosive exercise were examined. Eight subjects performed nonfatiguing bouts of single-legged drop jumps and rebound jumps on a force sledge apparatus. Measures of flight time, reactive strength index, peak vertical force, and vertical leg-spring stiffness were obtained for 3 drop jumps and 3 rebound jumps on both legs. Subjects utilized a stiffer leg spring and a more explosive jumping action in the nonpreferred leg when performing a cyclical rebound jumping task in comparison to a single drop jump task (observed through differences in vertical leg-spring stiffness, peak vertical force, and reactive strength index, p < 0.05). The preferred leg performed equally well in both tasks. Between-leg analysis showed no differences in dependent variables between the preferred and the nonpreferred leg in the rebound jumping protocol. However, the drop jump protocol showed significant performance differences, with flight time and reactive strength index greater in the preferred leg than the nonpreferred leg (p < 0.05). We hypothesize that, throughout the lifespan, both legs are equally trained in cyclical rebound jumping tasks through running. However, because a preferred leg must be selected when performing any one-off, single-legged jump, imbalances in this specific task develop over time with consistent selection of a preferred jumping leg. The data demonstrate that the rebound jump protocol is representative of the symmetrical mechanics of forward running and that leg-spring stiffness is modulated depending on the demands of the specific task involved. Strength and conditioning practitioners should give careful consideration to appropriate jump protocol selection and should exercise caution when comparing laboratory results to data gathered in field testing. PMID:17313262

  6. Modelling muscle spindle dynamics for a proprioceptive prosthesis.

    PubMed

    Williams, Ian; Constandinou, Timothy G

    2013-01-01

    Muscle spindles are found throughout our skeletal muscle tissue and continuously provide us with a sense of our limbs' position and motion (proprioception). This paper advances a model for generating artificial muscle spindle signals for a prosthetic limb, with the aim of one day providing amputees with a sense of feeling in their artificial limb. By utilising the Opensim biomechanical modelling package the relationship between a joint's angle and the length of surrounding muscles is estimated for a prosthetic limb. This is then applied to the established Mileusnic model to determine the associated muscle spindle firing pattern. This complete system model is then reduced to allow for a computationally efficient hardware implementation. This reduction is achieved with minimal impact on accuracy by selecting key mono-articular muscles and fitting equations to relate joint angle to muscle length. Parameter values fitting the Mileusnic model to human spindles are then proposed and validated against previously published human neural recordings. Finally, a model for fusimotor signals is also proposed based on data previously recorded from reduced animal experiments.

  7. A comparison of static and dynamic optimization muscle force predictions during wheelchair propulsion.

    PubMed

    Morrow, Melissa M; Rankin, Jeffery W; Neptune, Richard R; Kaufman, Kenton R

    2014-11-01

    The primary purpose of this study was to compare static and dynamic optimization muscle force and work predictions during the push phase of wheelchair propulsion. A secondary purpose was to compare the differences in predicted shoulder and elbow kinetics and kinematics and handrim forces. The forward dynamics simulation minimized differences between simulated and experimental data (obtained from 10 manual wheelchair users) and muscle co-contraction. For direct comparison between models, the shoulder and elbow muscle moment arms and net joint moments from the dynamic optimization were used as inputs into the static optimization routine. RMS errors between model predictions were calculated to quantify model agreement. There was a wide range of individual muscle force agreement that spanned from poor (26.4% Fmax error in the middle deltoid) to good (6.4% Fmax error in the anterior deltoid) in the prime movers of the shoulder. The predicted muscle forces from the static optimization were sufficient to create the appropriate motion and joint moments at the shoulder for the push phase of wheelchair propulsion, but showed deviations in the elbow moment, pronation-supination motion and hand rim forces. These results suggest the static approach does not produce results similar enough to be a replacement for forward dynamics simulations, and care should be taken in choosing the appropriate method for a specific task and set of constraints. Dynamic optimization modeling approaches may be required for motions that are greatly influenced by muscle activation dynamics or that require significant co-contraction. PMID:25282075

  8. A comparison of static and dynamic optimization muscle force predictions during wheelchair propulsion.

    PubMed

    Morrow, Melissa M; Rankin, Jeffery W; Neptune, Richard R; Kaufman, Kenton R

    2014-11-01

    The primary purpose of this study was to compare static and dynamic optimization muscle force and work predictions during the push phase of wheelchair propulsion. A secondary purpose was to compare the differences in predicted shoulder and elbow kinetics and kinematics and handrim forces. The forward dynamics simulation minimized differences between simulated and experimental data (obtained from 10 manual wheelchair users) and muscle co-contraction. For direct comparison between models, the shoulder and elbow muscle moment arms and net joint moments from the dynamic optimization were used as inputs into the static optimization routine. RMS errors between model predictions were calculated to quantify model agreement. There was a wide range of individual muscle force agreement that spanned from poor (26.4% Fmax error in the middle deltoid) to good (6.4% Fmax error in the anterior deltoid) in the prime movers of the shoulder. The predicted muscle forces from the static optimization were sufficient to create the appropriate motion and joint moments at the shoulder for the push phase of wheelchair propulsion, but showed deviations in the elbow moment, pronation-supination motion and hand rim forces. These results suggest the static approach does not produce results similar enough to be a replacement for forward dynamics simulations, and care should be taken in choosing the appropriate method for a specific task and set of constraints. Dynamic optimization modeling approaches may be required for motions that are greatly influenced by muscle activation dynamics or that require significant co-contraction.

  9. Biometry of the ciliary muscle during dynamic accommodation assessed with OCT

    NASA Astrophysics Data System (ADS)

    Ruggeri, Marco; Hernandez, Victor; de Freitas, Carolina; Manns, Fabrice; Parel, Jean-Marie

    2014-02-01

    Little is known about the structural changes of the ciliary muscle with age and how it may contribute to presbyopia. Optical coherence tomography (OCT) has been used to perform ciliary muscle biometry at different age and accommodative states with low resolution and speed. Dynamic imaging and accurate biometry of the ciliary muscle requires high-speed, high-resolution and correction of the OCT image distortions. We integrate an existing custom-made Spectral Domain OCT (SD-OCT) platform working at 840nm for biometry of the human eye with a SD-OCT system working at 1325nm that enables high-speed and high-resolution transscleral imaging of the ciliary muscle dynamically during accommodation and we developed an algorithm to provide corrected thickness measurements of the ciliary muscle.

  10. Myoneural necrosis following high-frequency electrical stimulation of the cast-immobilized rabbit hindlimb

    NASA Technical Reports Server (NTRS)

    Friden, J.; Lieber, R. L.; Myers, R. R.; Powell, H. C.; Hargens, A. R.

    1989-01-01

    The morphological and physiological effects of 4 weeks of high-frequency electrical stimulation (1 h/day, 5 days/week) on cast-immobilized rabbit hindlimbs were investigated in the tibialis anterior muscle and peroneal nerve. In 2 out of 6 animals, high-frequency stimulation with immobilization caused muscle fiber death, internalization of muscle fiber nuclei, connective tissue proliferation, inflammatory response, altered fiber size distribution and variable staining intensities. The fast-twitch fibers were predominantly affected. Two of six peripheral nerves subjected to immobilization and stimulation showed severe damage. Tetanic forces were significantly reduced in the affected muscles. Therefore, the immobilization and high-frequency stimulation may be detrimental to myoneural structure and function and, thus, this combination of therapies should be applied conservatively.

  11. The role of the polyol pathway in acute kidney injury caused by hindlimb ischaemia in mice.

    PubMed

    Yagihashi, Soroku; Mizukami, Hiroki; Ogasawara, Saori; Yamagishi, Shin-Ichiro; Nukada, Hitoshi; Kato, Noriaki; Hibi, Chihiro; Chung, Sookja; Chung, Stephen

    2010-04-01

    The polyol pathway, a collateral glycolytic process, previously considered to be active in high glucose milieu, has recently been proposed to play a crucial role in ischaemia/reperfusion tissue injury. In this study, we explored the role of the polyol pathway in acute kidney injury (AKI), a life-threatening condition, caused by hindlimb ischaemia, and determined if inhibition of the polyol pathway by aldose reductase (AR) inhibitor is beneficial for this serious disorder. Mice 8 weeks of age rendered hindlimb ischaemic for 3 h by the clipping of major supporting arteries revealed marked muscle necrosis with accumulation of sorbitol and fructose in ischaemic muscles. Serum concentrations of blood urea nitrogen (BUN), creatinine phosphokinase (CPK), creatinine, tumour necrosis factor (TNF)-alpha as well as interleukin (IL)-6 were all elevated in these mice. Treatment with AR inhibitor (ARI) effectively suppressed muscle necrosis and accompanying inflammatory reactions and prevented renal failure. Similar to ARI-treated mice, AR-deficient mice were protected from severe ischaemic limb injury and renal failure, showing only modest muscle necrosis and significant suppression of serum markers of renal failure and inflammation. Thus, these findings suggest that the polyol pathway is implicated in AKI caused by ischaemic limb injury and that AR may be a potential therapeutic target for this condition. PMID:20112370

  12. Decrease in Muscle Contraction Time Complements Neural Maturation in the Development of Dynamic Manipulation

    PubMed Central

    Dayanidhi, Sudarshan; Kutch, Jason J.

    2013-01-01

    Developmental improvements in dynamic manipulation abilities are typically attributed to neural maturation, such as myelination of corticospinal pathways, neuronal pruning, and synaptogenesis. However the contributions from changes in the peripheral motor system are less well understood. Here we investigated whether there are developmental changes in muscle activation-contraction dynamics and whether these changes contribute to improvements in dynamic manipulation in humans. We compared pinch strength, dynamic manipulation ability, and contraction time of the first dorsal interosseous muscle in typically developing preadolescent, adolescent, and young adults. Both strength and dynamic manipulation ability increased with age (p < 0.0001 and p < 0.00001, respectively). Surprisingly, adults had a 33% lower muscle contraction time compared with preadolescents (p < 0.01), and contraction time showed a significant (p < 0.005) association with dynamic manipulation abilities. Whereas decreases in muscle contraction time during development have been reported in the animal literature, our finding, to our knowledge, is the first report of this phenomenon in humans and the first finding of its association with manipulation. Consequently, the changes in the muscle contractile properties could be an important complement to neural maturation in the development of dynamic manipulation. These findings have important implications for understanding central and peripheral contributors to deficits in manipulation in atypical development, such as in children with cerebral palsy. PMID:24048835

  13. Muscle stimulation waveform timing patterns for upper and lower leg muscle groups to increase muscular endurance in functional electrical stimulation pedaling using a forward dynamic model.

    PubMed

    Hakansson, Nils A; Hull, M L

    2009-09-01

    Functional electrical stimulation (FES) of pedaling provides a means by which individuals with spinal cord injury can obtain cardiorespiratory exercise. However, the early onset of muscle fatigue is a limiting factor in the cardiorespiratory exercise obtained while pedaling an FES ergometer. One objective of this study was to determine muscle excitation timing patterns to increase muscle endurance in FES pedaling for three upper leg muscle groups and to compare these timing patterns to those used in a commercially available FES ergometer. The second objective was to determine excitation timing patterns for a lower leg muscle group in conjunction with the three upper leg muscle groups. The final objective was to determine the mechanical energy contributions of each of the muscle groups to drive the crank. To fulfill these objectives, we developed a forward dynamic simulation of FES pedaling to determine electrical stimulation on and off times that minimize the muscle stress-time integral of the stimulated muscles. The computed electrical stimulation on and off times differed from those utilized by a commercially available FES ergometer and resulted in 17% and 11% decrease in the muscle stress-time integral for the three upper leg muscle groups and four upper and lower leg muscle groups, respectively. Also, the duration of muscle activation by the hamstrings increased by 5% over a crank cycle for the computed stimulation on and off times, and the mechanical energy generated by the hamstrings increased by 20%. The lower leg muscle group did not generate sufficient mechanical energy to reduce the energy contributions of the upper leg muscle groups. The computed stimulation on and off times could prolong FES pedaling, and thereby provide improved cardiorespiratory and muscle training outcomes for individuals with spinal cord injury. Including the lower leg muscle group in FES pedaling could increase cardiorespiratory demand while not affecting the endurance of the

  14. Muscle stimulation waveform timing patterns for upper and lower leg muscle groups to increase muscular endurance in functional electrical stimulation pedaling using a forward dynamic model.

    PubMed

    Hakansson, Nils A; Hull, M L

    2009-09-01

    Functional electrical stimulation (FES) of pedaling provides a means by which individuals with spinal cord injury can obtain cardiorespiratory exercise. However, the early onset of muscle fatigue is a limiting factor in the cardiorespiratory exercise obtained while pedaling an FES ergometer. One objective of this study was to determine muscle excitation timing patterns to increase muscle endurance in FES pedaling for three upper leg muscle groups and to compare these timing patterns to those used in a commercially available FES ergometer. The second objective was to determine excitation timing patterns for a lower leg muscle group in conjunction with the three upper leg muscle groups. The final objective was to determine the mechanical energy contributions of each of the muscle groups to drive the crank. To fulfill these objectives, we developed a forward dynamic simulation of FES pedaling to determine electrical stimulation on and off times that minimize the muscle stress-time integral of the stimulated muscles. The computed electrical stimulation on and off times differed from those utilized by a commercially available FES ergometer and resulted in 17% and 11% decrease in the muscle stress-time integral for the three upper leg muscle groups and four upper and lower leg muscle groups, respectively. Also, the duration of muscle activation by the hamstrings increased by 5% over a crank cycle for the computed stimulation on and off times, and the mechanical energy generated by the hamstrings increased by 20%. The lower leg muscle group did not generate sufficient mechanical energy to reduce the energy contributions of the upper leg muscle groups. The computed stimulation on and off times could prolong FES pedaling, and thereby provide improved cardiorespiratory and muscle training outcomes for individuals with spinal cord injury. Including the lower leg muscle group in FES pedaling could increase cardiorespiratory demand while not affecting the endurance of the

  15. Planar Covariation of Hindlimb and Forelimb Elevation Angles during Terrestrial and Aquatic Locomotion of Dogs

    PubMed Central

    Catavitello, Giovanna; Ivanenko, Yuri P.; Lacquaniti, Francesco

    2015-01-01

    The rich repertoire of locomotor behaviors in quadrupedal animals requires flexible inter-limb and inter-segmental coordination. Here we studied the kinematic coordination of different gaits (walk, trot, gallop, and swim) of six dogs (Canis lupus familiaris) and, in particular, the planar covariation of limb segment elevation angles. The results showed significant variations in the relative duration of rearward limb movement, amplitude of angular motion, and inter-limb coordination, with gait patterns ranging from a lateral sequence of footfalls during walking to a diagonal sequence in swimming. Despite these differences, the planar law of inter-segmental coordination was maintained across different gaits in both forelimbs and hindlimbs. Notably, phase relationships and orientation of the covariation plane were highly limb specific, consistent with the functional differences in their neural control. Factor analysis of published muscle activity data also demonstrated differences in the characteristic timing of basic activation patterns of the forelimbs and hindlimbs. Overall, the results demonstrate that the planar covariation of inter-segmental coordination has emerged for both fore- and hindlimbs and all gaits, although in a limb-specific manner. PMID:26218076

  16. Shifts in a single muscle's control potential of body dynamics are determined by mechanical feedback

    PubMed Central

    Sponberg, Simon; Libby, Thomas; Mullens, Chris H.; Full, Robert J.

    2011-01-01

    Muscles are multi-functional structures that interface neural and mechanical systems. Muscle work depends on a large multi-dimensional space of stimulus (neural) and strain (mechanical) parameters. In our companion paper, we rewrote activation to individual muscles in intact, behaving cockroaches (Blaberus discoidalis L.), revealing a specific muscle's potential to control body dynamics in different behaviours. Here, we use those results to provide the biologically relevant parameters for in situ work measurements. We test four hypotheses about how muscle function changes to provide mechanisms for the observed control responses. Under isometric conditions, a graded increase in muscle stress underlies its linear actuation during standing behaviours. Despite typically absorbing energy, this muscle can recruit two separate periods of positive work when controlling running. This functional change arises from mechanical feedback filtering a linear increase in neural activation into nonlinear work output. Changing activation phase again led to positive work recruitment, but at different times, consistent with the muscle's ability to also produce a turn. Changes in muscle work required considering the natural sequence of strides and separating swing and stance contributions of work. Both in vivo control potentials and in situ work loops were necessary to discover the neuromechanical coupling enabling control. PMID:21502130

  17. Chest wall dynamics and muscle recruitment during professional flute playing.

    PubMed

    Cossette, Isabelle; Monaco, Pierpaolo; Aliverti, Andrea; Macklem, Peter T

    2008-02-01

    Respiratory parameters and sound were recorded during professional flute playing in order to assess what physiological processes were associated with the control of sound production that results in 'breath support' which in turn is associated with high quality playing. Four standing young professional flautists played flute excerpts with and without breath support. Recordings included optoelectronic plethysmographic measurements of chest wall volume (V(cw)) and its compartments, surface electromyography of the scalene, lateral abdominal, rectus abdominus, parasternal and sternocleidomastoid muscles, mouth pressure, and sound. Flow was estimated from differentiating V(cw) during playing. Results showed that flute support entails antagonistic contraction of non-diaphragmatic inspiratory muscles that tends to hold the rib cage at higher lung volume. This relieves the expiratory muscles from the task of producing the right mouth pressure, especially at the end of the phrases, so they can contribute more to the finer control of mouth pressure modulations required for high quality playing.

  18. Dense distributed processing in a hindlimb scratch motor network.

    PubMed

    Guzulaitis, Robertas; Alaburda, Aidas; Hounsgaard, Jorn

    2014-08-01

    In reduced preparations, hindlimb movements can be generated by a minimal network of neurons in the limb innervating spinal segments. The network of neurons that generates real movements is less well delineated. In an ex vivo carapace-spinal cord preparation from adult turtles (Trachemys scripta elegans), we show that ventral horn interneurons in mid-thoracic spinal segments are functionally integrated in the hindlimb scratch network. First, mid-thoracic interneurons receive intense synaptic input during scratching and behave like neurons in the hindlimb enlargement. Second, some mid-thoracic interneurons activated during scratching project descending axons toward the hindlimb enlargement. Third, elimination of mid-thoracic segments leads to a weakening of scratch rhythmicity. We conclude that densely innervated interneurons in mid-thoracic segments contribute to hindlimb scratching and may be part of a distributed motor network that secures motor coherence.

  19. Local dynamic stability of spine muscle activation and stiffness patterns during repetitive lifting.

    PubMed

    Graham, Ryan B; Brown, Stephen H M

    2014-12-01

    To facilitate stable trunk kinematics, humans must generate appropriate motor patterns to effectively control muscle force and stiffness and respond to biomechanical perturbations and/or neuromuscular control errors. Thus, it is important to understand physiological variables such as muscle force and stiffness, and how these relate to the downstream production of stable spine and trunk movements. This study was designed to assess the local dynamic stability of spine muscle activation and rotational stiffness patterns using Lyapunov analyses, and relationships to the local dynamic stability of resulting spine kinematics, during repetitive lifting and lowering at varying combinations of lifting load and rate. With an increase in the load lifted at a constant rate there was a trend for decreased local dynamic stability of spine muscle activations and the muscular contributions to spine rotational stiffness; although the only significant change was for the full state space muscle activation stability (p < 0.05). With an increase in lifting rate with a constant load there was a significant decrease in the local dynamic stability of spine muscle activations and the muscular contributions to spine rotational stiffness (p ≤ 0.001 for all measures). These novel findings suggest that the stability of motor inputs and the muscular contributions to spine rotational stiffness can be altered by external task demands (load and lifting rate), and therefore are important variables to consider when assessing the stability of the resulting kinematics.

  20. An in vitro spinal cord-hindlimb preparation for studying behaviorally relevant rat locomotor function.

    PubMed

    Hayes, Heather Brant; Chang, Young-Hui; Hochman, Shawn

    2009-02-01

    Although the spinal cord contains the pattern-generating circuitry for producing locomotion, sensory feedback reinforces and refines the spatiotemporal features of motor output to match environmental demands. In vitro preparations, such as the isolated rodent spinal cord, offer many advantages for investigating locomotor circuitry, but they lack the natural afferent feedback provided by ongoing locomotor movements. We developed a novel preparation consisting of an isolated in vitro neonatal rat spinal cord oriented dorsal-up with intact hindlimbs free to step on a custom-built treadmill. This preparation combines the neural accessibility of in vitro preparations with the modulatory influence of sensory feedback from physiological hindlimb movement. Locomotion induced by N-methyl D-aspartate and serotonin showed kinematics similar to that of normal adult rat locomotion. Changing orientation and ground interaction (dorsal-up locomotion vs ventral-up air-stepping) resulted in significant kinematic and electromyographic changes that were comparable to those reported under similar mechanical conditions in vivo. We then used two mechanosensory perturbations to demonstrate the influence of sensory feedback on in vitro motor output patterns. First, swing assistive forces induced more regular, robust muscle activation patterns. Second, altering treadmill speed induced corresponding changes in stride frequency, confirming that changes in sensory feedback can alter stride timing in vitro. In summary, intact hindlimbs in vitro can generate behaviorally appropriate locomotor kinematics and responses to sensory perturbations. Future studies combining the neural and chemical accessibility of the in vitro spinal cord with the influence of behaviorally appropriate hindlimb movements will provide further insight into the operation of spinal motor pattern-generating circuits.

  1. The Pleiotropic Effect of Physical Exercise on Mitochondrial Dynamics in Aging Skeletal Muscle

    PubMed Central

    Barbieri, Elena; Agostini, Deborah; Polidori, Emanuela; Potenza, Lucia; Guescini, Michele; Lucertini, Francesco; Annibalini, Giosuè; Stocchi, Laura; De Santi, Mauro; Stocchi, Vilberto

    2015-01-01

    Decline in human muscle mass and strength (sarcopenia) is one of the principal hallmarks of the aging process. Regular physical exercise and training programs are certain powerful stimuli to attenuate the physiological skeletal muscle alterations occurring during aging and contribute to promote health and well-being. Although the series of events that led to these muscle adaptations are poorly understood, the mechanisms that regulate these processes involve the “quality” of skeletal muscle mitochondria. Aerobic/endurance exercise helps to maintain and improve cardiovascular fitness and respiratory function, whereas strength/resistance-exercise programs increase muscle strength, power development, and function. Due to the different effect of both exercises in improving mitochondrial content and quality, in terms of biogenesis, dynamics, turnover, and genotype, combined physical activity programs should be individually prescribed to maximize the antiaging effects of exercise. PMID:25945152

  2. Precise Muscle Selection Using Dynamic Polyelectromyography for Treatment of Post-stroke Dystonia: A Case Report

    PubMed Central

    2016-01-01

    Dystonia has a wide range of causes, but treatment of dystonia is limited to minimizing the symptoms as there is yet no successful treatment for its cause. One of the optimal treatment methods for dystonia is chemodenervation using botulinum toxin type A (BTX-A), alcohol injection, etc., but its success depends on how precisely the dystonic muscle is selected. Here, we reported a successful experience in a 49-year-old post-stroke female patient who showed paroxysmal repetitive contractions involving the right leg, which may be of dystonic nature. BTX-A and alcohol were injected into the muscles which were identified by dynamic polyelectromyography. After injection, the dystonic muscle spasm, cramping pain, and the range of motion of the affected lower limb improved markedly, and she was able to walk independently indoors. In such a case, dynamic polyelectromyography may be a useful method for selecting the dominant dystonic muscles. PMID:27446795

  3. Obtaining maximum muscle excitation for normalizing shoulder electromyography in dynamic contractions.

    PubMed

    Hodder, Joanne N; Keir, Peter J

    2013-10-01

    Muscle specific maximal voluntary isometric contractions (MVIC) are commonly used to elicit reference amplitudes to normalize electromyographic signals (EMG). It has been questioned whether this is appropriate for normalizing EMG from dynamic contractions. This study compares EMG amplitude when shoulder muscle activity from dynamic contractions is normalized to isometric and isokinetic maximal excitation as well as a hybrid approach currently used in our laboratory. Anterior, middle and posterior deltoid, upper and lower trapezius, pectoralis major, latissimus dorsi and infraspinatus were monitored during (1) manually resisted MVICs, and (2) maximum voluntary dynamic concentric contractions (MVDC) on an isokinetic dynamometer. Dynamic contractions were performed (a) at 30°/s about the longitudinal, frontal and sagittal axes of the shoulder, and (b) during manual bi-rotation of a tilted wheel at 120°/s. EMG from the wheel task was normalized to the maximum excitation from (i) the muscle specific MVIC, (ii) from any MVIC (MVICALL), (iii) for any MVDC, (iv) from any exertion (maximum experimental excitation, MEE). Mean EMG from the wheel task was up to 45% greater when normalized to muscle specific isometric contractions (method i) than when normalized to MEE (method iv). Seventy-five percent of MEE's occurred during MVDCs. This study presents an 20 useful and effective process for obtaining the greatest excitation from the shoulder muscles when normalizing dynamic efforts.

  4. Determine the effect of neck muscle fatigue on dynamic visual acuity in healthy young adults.

    PubMed

    Al Saif, Amer A; Al Senany, Samira

    2015-01-01

    [Purpose] The aim of this study was to determine whether neck muscle fatigue affects dynamic visual acuity in healthy young participants. [Subjects and Methods] This study was a double-blinded, prospective, randomized, controlled trial. Thirty healthy young subjects (ages 21 to 30 years) participated in the study. Participants were randomly divided into an experimental group (n=15) and a control group (n=15). The experimental group performed an exercise designed to induce neck muscle fatigue and the control group preformed non-fatiguing sham exercises. [Results] There were significant differences in mean dynamic visual acuity between the two groups (0.26±0.11 LogMar versus 0.003±0.02 LogMar). Subjects in the experimental group showed a significant decline in their dynamic visual acuity compared with the control group. Dynamic visual acuity strongly correlated with neck muscle fatigue (r = 0.79). No significant differences in joint position error were observed between the two groups and no significant correlations between joint position error and neck muscle fatigue were observed (r = 0.23). [Conclusion] The results of this study suggest that neck muscle fatigue negatively impacts dynamic visual acuity. Although not statistically significant, cervical spine proprioception as measured by the joint position error in the experimental group was diminished after fatigue.

  5. Increased Insulin Sensitivity and Distorted Mitochondrial Adaptations during Muscle Unloading

    PubMed Central

    Qi, Zhengtang; Zhang, Yuan; Guo, Wei; Ji, Liu; Ding, Shuzhe

    2012-01-01

    We aimed to further investigate mitochondrial adaptations to muscle disuse and the consequent metabolic disorders. Male rats were submitted to hindlimb unloading (HU) for three weeks. Interestingly, HU increased insulin sensitivity index (ISI) and decreased blood level of triglyceride and insulin. In skeletal muscle, HU decreased expression of pyruvate dehydrogenase kinase 4 (PDK4) and its protein level in mitochondria. HU decreased mtDNA content and mitochondrial biogenesis biomarkers. Dynamin-related protein (Drp1) in mitochondria and Mfn2 mRNA level were decreased significantly by HU. Our findings provide more extensive insight into mitochondrial adaptations to muscle disuse, involving the shift of fuel utilization towards glucose, the decreased mitochondrial biogenesis and the distorted mitochondrial dynamics. PMID:23443131

  6. Fatigability and blood flow in the rat gastrocnemius-plantaris-soleus after hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Mcdonald, K. S.; Delp, M. D.; Fitts, R. H.

    1992-01-01

    The hypothesis that hindlimb suspension (HS) increases the fatigability of the soleus during intense contractile activity and that the increased fatigue is associated with a reduced muscle blood flow was tested using caged control rats and rats subjected to HS for 15 days. After 15 days, either the soleus or the gastrocnemius-plantaris-soleus (G-P-S) muscle group was stimulated in situ (10 min at 100 Hz, 100 ms trains at 120/min), and in the G-P-S preparation, blood flow was measured with radiolabeled microspheres before and at 2 min and 10 min after the start of contractile activity. The results indicate that 15 days of HS resulted in increased fatigability of the soleus, but the effect was not caused by a reduced muscle blood flow.

  7. Forms of forward quadrupedal locomotion. III. A comparison of posture, hindlimb kinematics, and motor patterns for downslope and level walking.

    PubMed

    Smith, J L; Carlson-Kuhta, P; Trank, T V

    1998-04-01

    To gain further insight into the neural mechanisms for different forms of quadrupedal walking, data on postural orientation, hindlimb kinematics, and motor patterns were assessed for four grades of downslope walking, from 25% (14 degrees slope) to 100% (45 degrees), and compared with data from level and downslope walking at five grades (5-25%) on the treadmill (0.6 m/s). Kinematic data were obtained by digitizing ciné film, and electromyograms (EMGs) synchronized with kinematic records were taken from 13 different hindlimb muscles. At grades from 25 to 75%, cycle periods were similar, but at the steepest grade the cycle was shorter because of a reduced stance phase. Paw-contact sequences at all grades were consistent with lateral-sequence walking, but pace walking often occurred at the steepest grades. The cats crouched at the steeper grades, and crouching was associated with changes in fore- and hindlimb orientation that were consistent with increasing braking forces and decreasing propulsive forces during stance. The average ranges of motion at the hindlimb joints, except at the hip, were often different at the two steepest slopes. During swing, the range of knee- and ankle-joint flexion decreased, and the range and duration of extension increased at the ankle joint to lower the paw downward for contact. During stance the range of flexion during yield increased at the ankle joint, and the range of extension decreased at the knee and metatarsophalangeal joints. Downslope walking was also associated with EMG changes for several muscles. The hip extensors were not active during stance; instead, hip flexors were active, presumably to slow the rate of hip extension. Although ankle extensors were active during stance, their burst durations were truncated and centered around paw contact. Ankle flexors were active after midstance at the steeper slopes before the need to initiate swing, whereas flexor and extensor digit muscles were coactive throughout stance. Overall

  8. An action potential-driven model of soleus muscle activation dynamics for locomotor-like movements

    PubMed Central

    Kim, Hojeong; Sandercock, Thomas G.; Heckman, C. J.

    2016-01-01

    Objective The goal of this study was to develop a physiologically plausible, computationally robust model for the muscle activation dynamics (A(t)) under physiologically relevant excitation and movement. Approach The interaction of excitation and movement on A(t) was investigated comparing the force production between a cat soleus muscle and its Hill-type model. For capturing A(t) under excitation and movement variation, a modular modeling framework was proposed comprising of 3 compartments: (1) spikes-to-[Ca2+]; (2) [Ca2+]-to-A; and (3) A-to-force transformation. The individual signal transformations were modeled based on physiological factors so that the parameter values could be separately determined for individual modules directly based on experimental data. Main results The strong dependency of A(t) on excitation frequency and muscle length was found during both isometric and dynamically-moving contractions. The identified dependencies of A(t) under the static and dynamic conditions could be incorporated in the modular modeling framework by modulating the model parameters as a function of movement input. The new modeling approach was also applicable to cat soleus muscles producing waveforms independent of those used to set the model parameters. Significance This study provides a modeling framework for spike-driven muscle responses during movement, that is suitable not only for insights into molecular mechanisms underlying muscle behaviors but also for large scale simulations. PMID:26087477

  9. An action potential-driven model of soleus muscle activation dynamics for locomotor-like movements

    NASA Astrophysics Data System (ADS)

    Kim, Hojeong; Sandercock, Thomas G.; Heckman, C. J.

    2015-08-01

    Objective. The goal of this study was to develop a physiologically plausible, computationally robust model for muscle activation dynamics (A(t)) under physiologically relevant excitation and movement. Approach. The interaction of excitation and movement on A(t) was investigated comparing the force production between a cat soleus muscle and its Hill-type model. For capturing A(t) under excitation and movement variation, a modular modeling framework was proposed comprising of three compartments: (1) spikes-to-[Ca2+]; (2) [Ca2+]-to-A; and (3) A-to-force transformation. The individual signal transformations were modeled based on physiological factors so that the parameter values could be separately determined for individual modules directly based on experimental data. Main results. The strong dependency of A(t) on excitation frequency and muscle length was found during both isometric and dynamically-moving contractions. The identified dependencies of A(t) under the static and dynamic conditions could be incorporated in the modular modeling framework by modulating the model parameters as a function of movement input. The new modeling approach was also applicable to cat soleus muscles producing waveforms independent of those used to set the model parameters. Significance. This study provides a modeling framework for spike-driven muscle responses during movement, that is suitable not only for insights into molecular mechanisms underlying muscle behaviors but also for large scale simulations.

  10. Effect of cadence regulation on muscle activation patterns during robot assisted gait: a dynamic simulation study.

    PubMed

    Hussain, Shahid; Xie, Sheng Q; Jamwal, Prashant K

    2013-03-01

    Cadence or stride frequency is an important parameter being controlled in gait training of neurologically impaired subjects. The aim of this study was to examine the effects of cadence variation on muscle activation patterns during robot assisted unimpaired gait using dynamic simulations. A twodimensional (2-D) musculoskeletal model of human gait was developed considering eight major muscle groups along with existing ground contact force (GCF) model. A 2-D model of a robotic orthosis was also developed which provides actuation to the hip, knee and ankle joints in the sagittal plane to guide subjects limbs on reference trajectories. A custom inverse dynamics algorithm was used along with a quadratic minimization algorithm to obtain a feasible set of muscle activation patterns. Predicted patterns of muscle activations during slow, natural and fast cadence were compared and the mean muscle activations were found to be increasing with an increase in cadence. The proposed dynamic simulation provide important insight into the muscle activation variations with change in cadence during robot assisted gait and provide the basis for investigating the influence of cadence regulation on neuromuscular parameters of interest during robot assisted gait.

  11. Three-Dimensional Muscle Architecture and Comprehensive Dynamic Properties of Rabbit Gastrocnemius, Plantaris and Soleus: Input for Simulation Studies

    PubMed Central

    Siebert, Tobias; Leichsenring, Kay; Rode, Christian; Wick, Carolin; Stutzig, Norman; Schubert, Harald; Blickhan, Reinhard; Böl, Markus

    2015-01-01

    The vastly increasing number of neuro-muscular simulation studies (with increasing numbers of muscles used per simulation) is in sharp contrast to a narrow database of necessary muscle parameters. Simulation results depend heavily on rough parameter estimates often obtained by scaling of one muscle parameter set. However, in vivo muscles differ in their individual properties and architecture. Here we provide a comprehensive dataset of dynamic (n = 6 per muscle) and geometric (three-dimensional architecture, n = 3 per muscle) muscle properties of the rabbit calf muscles gastrocnemius, plantaris, and soleus. For completeness we provide the dynamic muscle properties for further important shank muscles (flexor digitorum longus, extensor digitorum longus, and tibialis anterior; n = 1 per muscle). Maximum shortening velocity (normalized to optimal fiber length) of the gastrocnemius is about twice that of soleus, while plantaris showed an intermediate value. The force-velocity relation is similar for gastrocnemius and plantaris but is much more bent for the soleus. Although the muscles vary greatly in their three-dimensional architecture their mean pennation angle and normalized force-length relationships are almost similar. Forces of the muscles were enhanced in the isometric phase following stretching and were depressed following shortening compared to the corresponding isometric forces. While the enhancement was independent of the ramp velocity, the depression was inversely related to the ramp velocity. The lowest effect strength for soleus supports the idea that these effects adapt to muscle function. The careful acquisition of typical dynamical parameters (e.g. force-length and force-velocity relations, force elongation relations of passive components), enhancement and depression effects, and 3D muscle architecture of calf muscles provides valuable comprehensive datasets for e.g. simulations with neuro-muscular models, development of more realistic muscle models, or

  12. Hindlimb unloading elicits anhedonia and sympathovagal imbalance.

    PubMed

    Moffitt, Julia A; Grippo, Angela J; Beltz, Terry G; Johnson, Alan Kim

    2008-10-01

    The hindlimb-unloaded (HU) rat model elicits cardiovascular deconditioning and simulates the physiological adaptations to microgravity or prolonged bed rest in humans. Although psychological deficits have been documented following bed rest and spaceflight in humans, few studies have explored the psychological effects of cardiovascular deconditioning in animal models. Given the bidirectional link established between cardiac autonomic imbalance and psychological depression in both humans and in animal models, we hypothesized that hindlimb unloading would elicit an alteration in sympathovagal tone and behavioral indexes of psychological depression. Male, Sprague-Dawley rats confined to 14 days of HU displayed anhedonia (a core feature of human depression) compared with casted control (CC) animals evidenced by reduced sucrose preference (CC: 81 +/- 2.9% baseline vs. HU: 58 +/- 4.5% baseline) and reduced (rightward shift) operant responding for rewarding electrical brain stimulation (CC: 4.4 +/- 0.3 muA vs. 7.3 +/- 1.0 muA). Cardiac autonomic blockade revealed elevated sympathetic [CC: -54 +/- 14.1 change in (Delta) beats/min vs. HU: -118 +/- 7.6 Delta beats/min] and reduced parasympathetic (CC: 45 +/- 11.8 Delta beats/min vs. HU: 8 +/- 7.3 Delta beats/min) cardiac tone in HU rats. Heart rate variability was reduced (CC: 10 +/- 1.4 ms vs. HU: 7 +/- 0.7 ms), and spectral analysis of blood pressure indicated loss of total, low-, and high-frequency power, consistent with attenuated baroreflex function. These data indicate that cardiovascular deconditioning results in sympathovagal imbalance and behavioral signs consistent with psychological depression. These findings further elucidate the pathophysiological link between cardiovascular diseases and affective disorders.

  13. Oral Dosing of Chemical Indicators for In Vivo Monitoring of Ca2+ Dynamics in Insect Muscle

    PubMed Central

    Ferdinandus; Arai, Satoshi; Ishiwata, Shin’ichi; Suzuki, Madoka; Sato, Hirotaka

    2015-01-01

    This paper proposes a remarkably facile staining protocol to visually investigate dynamic physiological events in insect tissues. We attempted to monitor Ca2+ dynamics during contraction of electrically stimulated living muscle. Advances in circuit miniaturization and insect neuromuscular physiology have enabled the hybridization of living insects and man-made electronic components, such as microcomputers, the result of which has been often referred as a Living Machine, Biohybrid, or Cyborg Insect. In order for Cyborg Insects to be of practical use, electrical stimulation parameters need to be optimized to induce desired muscle response (motor action) and minimize the damage in the muscle due to the electrical stimuli. Staining tissues and organs as well as measuring the dynamics of chemicals of interest in muscle should be conducted to quantitatively and systematically evaluate the effect of various stimulation parameters on the muscle response. However, existing staining processes require invasive surgery and/or arduous procedures using genetically encoded sensors. In this study, we developed a non-invasive and remarkably facile method for staining, in which chemical indicators can be orally administered (oral dosing). A chemical Ca2+ indicator was orally introduced into an insect of interest via food containing the chemical indicator and the indicator diffused from the insect digestion system to the target muscle tissue. We found that there was a positive relationship between the fluorescence intensity of the indicator and the frequency of electrical stimulation which indicates the orally dosed indicator successfully monitored Ca2+ dynamics in the muscle tissue. This oral dosing method has a potential to globally stain tissues including neurons, and investigating various physiological events in insects. PMID:25590329

  14. Oral dosing of chemical indicators for in vivo monitoring of Ca2+ dynamics in insect muscle.

    PubMed

    Ferdinandus; Arai, Satoshi; Ishiwata, Shin'ichi; Suzuki, Madoka; Sato, Hirotaka

    2015-01-01

    This paper proposes a remarkably facile staining protocol to visually investigate dynamic physiological events in insect tissues. We attempted to monitor Ca2+ dynamics during contraction of electrically stimulated living muscle. Advances in circuit miniaturization and insect neuromuscular physiology have enabled the hybridization of living insects and man-made electronic components, such as microcomputers, the result of which has been often referred as a Living Machine, Biohybrid, or Cyborg Insect. In order for Cyborg Insects to be of practical use, electrical stimulation parameters need to be optimized to induce desired muscle response (motor action) and minimize the damage in the muscle due to the electrical stimuli. Staining tissues and organs as well as measuring the dynamics of chemicals of interest in muscle should be conducted to quantitatively and systematically evaluate the effect of various stimulation parameters on the muscle response. However, existing staining processes require invasive surgery and/or arduous procedures using genetically encoded sensors. In this study, we developed a non-invasive and remarkably facile method for staining, in which chemical indicators can be orally administered (oral dosing). A chemical Ca2+ indicator was orally introduced into an insect of interest via food containing the chemical indicator and the indicator diffused from the insect digestion system to the target muscle tissue. We found that there was a positive relationship between the fluorescence intensity of the indicator and the frequency of electrical stimulation which indicates the orally dosed indicator successfully monitored Ca2+ dynamics in the muscle tissue. This oral dosing method has a potential to globally stain tissues including neurons, and investigating various physiological events in insects. PMID:25590329

  15. Cardiac supporting device using artificial rubber muscle: preliminary study to active dynamic cardiomyoplasty.

    PubMed

    Saito, Yoshiaki; Suzuki, Yasuyuki; Goto, Takeshi; Daitoku, Kazuyuki; Minakawa, Masahito; Fukuda, Ikuo

    2015-12-01

    Dynamic cardiomyoplasty is a surgical treatment that utilizes the patient's skeletal muscle to support circulation. To overcome the limitations of autologous skeletal muscles in dynamic cardiomyoplasty, we studied the use of a wrapped-type cardiac supporting device using pneumatic muscles. Four straight rubber muscles (Fluidic Muscle, FESTO, Esslingen, Germany) were used and connected to pressure sensors, solenoid valves, a controller and an air compressor. The driving force was compressed air. A proportional-integral-derivative system was employed to control the device movement. An overflow-type mock circulation system was used to analyze the power and the controllability of this new device. The device worked powerfully with pumped flow against afterload of 88 mmHg, and the beating rate and contraction/dilatation time were properly controlled using simple software. Maximum pressure inside the ventricle and maximum output were 187 mmHg and 546.5 ml/min, respectively, in the setting of 50 beats per minute, a contraction/dilatation ratio of 1:2, a preload of 18 mmHg, and an afterload of 88 mmHg. By changing proportional gain, contraction speed could be modulated. This study showed the efficacy and feasibility of a pneumatic muscle for use in a cardiac supporting device.

  16. sEMG wavelet-based indices predicts muscle power loss during dynamic contractions.

    PubMed

    González-Izal, M; Rodríguez-Carreño, I; Malanda, A; Mallor-Giménez, F; Navarro-Amézqueta, I; Gorostiaga, E M; Izquierdo, M

    2010-12-01

    The purpose of this study was to investigate the sensitivity of new surface electromyography (sEMG) indices based on the discrete wavelet transform to estimate acute exercise-induced changes on muscle power output during a dynamic fatiguing protocol. Fifteen trained subjects performed five sets consisting of 10 leg press, with 2 min rest between sets. sEMG was recorded from vastus medialis (VM) muscle. Several surface electromyographic parameters were computed. These were: mean rectified voltage (MRV), median spectral frequency (F(med)), Dimitrov spectral index of muscle fatigue (FI(nsm5)), as well as five other parameters obtained from the stationary wavelet transform (SWT) as ratios between different scales. The new wavelet indices showed better accuracy to map changes in muscle power output during the fatiguing protocol. Moreover, the new wavelet indices as a single parameter predictor accounted for 46.6% of the performance variance of changes in muscle power and the log-FI(nsm5) and MRV as a two-factor combination predictor accounted for 49.8%. On the other hand, the new wavelet indices proposed, showed the highest robustness in presence of additive white Gaussian noise for different signal to noise ratios (SNRs). The sEMG wavelet indices proposed may be a useful tool to map changes in muscle power output during dynamic high-loading fatiguing task.

  17. Biomechanics and muscle coordination of human walking: part II: lessons from dynamical simulations and clinical implications.

    PubMed

    Zajac, Felix E; Neptune, Richard R; Kautz, Steven A

    2003-02-01

    Principles of muscle coordination in gait have been based largely on analyses of body motion, ground reaction force and EMG measurements. However, data from dynamical simulations provide a cause-effect framework for analyzing these measurements; for example, Part I (Gait Posture, in press) of this two-part review described how force generation in a muscle affects the acceleration and energy flow among the segments. This Part II reviews the mechanical and coordination concepts arising from analyses of simulations of walking. Simple models have elucidated the basic multisegmented ballistic and passive mechanics of walking. Dynamical models driven by net joint moments have provided clues about coordination in healthy and pathological gait. Simulations driven by muscle excitations have highlighted the partial stability afforded by muscles with their viscoelastic-like properties and the predictability of walking performance when minimization of metabolic energy per unit distance is assumed. When combined with neural control models for exciting motoneuronal pools, simulations have shown how the integrative properties of the neuro-musculo-skeletal systems maintain a stable gait. Other analyses of walking simulations have revealed how individual muscles contribute to trunk support and progression. Finally, we discuss how biomechanical models and simulations may enhance our understanding of the mechanics and muscle function of walking in individuals with gait impairments.

  18. Biomechanics and muscle coordination of human walking. Part I: introduction to concepts, power transfer, dynamics and simulations.

    PubMed

    Zajac, Felix E; Neptune, Richard R; Kautz, Steven A

    2002-12-01

    Current understanding of how muscles coordinate walking in humans is derived from analyses of body motion, ground reaction force and EMG measurements. This is Part I of a two-part review that emphasizes how muscle-driven dynamics-based simulations assist in the understanding of individual muscle function in walking, especially the causal relationships between muscle force generation and walking kinematics and kinetics. Part I reviews the strengths and limitations of Newton-Euler inverse dynamics and dynamical simulations, including the ability of each to find the contributions of individual muscles to the acceleration/deceleration of the body segments. We caution against using the concept of biarticular muscles transferring power from one joint to another to infer muscle coordination principles because energy flow among segments, even the adjacent segments associated with the joints, cannot be inferred from computation of joint powers and segmental angular velocities alone. Rather, we encourage the use of dynamical simulations to perform muscle-induced segmental acceleration and power analyses. Such analyses have shown that the exchange of segmental energy caused by the forces or accelerations induced by a muscle can be fundamentally invariant to whether the muscle is shortening, lengthening, or neither. How simulation analyses lead to understanding the coordination of seated pedaling, rather than walking, is discussed in this first part because the dynamics of pedaling are much simpler, allowing important concepts to be revealed. We elucidate how energy produced by muscles is delivered to the crank through the synergistic action of other non-energy producing muscles; specifically, that a major function performed by a muscle arises from the instantaneous segmental accelerations and redistribution of segmental energy throughout the body caused by its force generation. Part II reviews how dynamical simulations provide insight into muscle coordination of walking.

  19. Effects of hindlimb unloading and bisphosphonates on the serum proteome of rats.

    PubMed

    Zhao, Yongdong; Fleet, James C; Adamec, Jiri; Terry, Doris E; Zhang, Xiang; Kemeh, Settor; Davisson, V Jo; Weaver, Connie M

    2007-10-01

    Hindlimb unloading has been used as a model for bone loss associated with extended bed rest or space travel. However, this model also reduces muscle mass and influences other biological systems. To evaluate the impact of hindlimb unloading on bone and overall health, we applied 2-D gel electrophoresis (2-DE)-based proteomics to serum samples collected from 24 5-month-old female rats that were treated for 2 weeks under three conditions: control, hindlimb unloading (HU) and unloading plus bisphosphonate (HUA) (n=8/group). Prior to the intervention, rats were injected with 3H-tetracycline to label bone surfaces. At the end of the experiment bone, urine, and serum samples were collected. As expected, HU reduced femur aBMD and BMC and increased daily urinary 3H-tetracycline (a measure of bone resorption rate) and these effects were reversed by bisphosphonate. In addition, serum osteocalcin and TRAP5b were decreased in the HUA compared to control and HU. Abundant proteins, albumin, IgG and transferrin were removed from serum samples prior to 2-DE analysis (n=5 analytical replicates). Statistical analysis of spot intensities revealed 53 differentially expressed spots among the 3 groups. Cluster analysis shows that 30 spots reflect changes unique to the HU group (i.e. potential bone biomarkers), 6 unique to HUA (i.e. drug related), and 17 common to HU and HUA (e.g. potential mental stress or muscle loss markers). Spots were identified by LC-MS/MS after in-gel trypsin digestion and were found to relate to a variety of physiological functions.

  20. Estimation of muscle activity using higher-order derivatives, static optimization, and forward-inverse dynamics.

    PubMed

    Yamasaki, Taiga; Idehara, Katsutoshi; Xin, Xin

    2016-07-01

    We propose a new method to estimate muscle activity in a straightforward manner with high accuracy and relatively small computational costs by using the external input of the joint angle and its first to fourth derivatives with respect to time. The method solves the inverse dynamics problem of the skeletal system, the forward dynamics problem of the muscular system, and the load-sharing problem of muscles as a static optimization of neural excitation signals. The external input including the higher-order derivatives is required for a calculation of constraints imposed on the load-sharing problem. The feasibility of the method is demonstrated by the simulation of a simple musculoskeletal model with a single joint. Moreover, the influences of the muscular dynamics, and the higher-order derivatives on the estimation of the muscle activity are demonstrated, showing the results when the time constants of the activation dynamics are very small, and the third and fourth derivatives of the external input are ignored, respectively. It is concluded that the method can have the potential to improve estimation accuracy of muscle activity of highly dynamic motions. PMID:27211782

  1. Synergist Ablation as a Rodent Model to Study Satellite Cell Dynamics in Adult Skeletal Muscle.

    PubMed

    Kirby, Tyler J; McCarthy, John J; Peterson, Charlotte A; Fry, Christopher S

    2016-01-01

    In adult skeletal muscles, satellite cells are the primary myogenic stem cells involved in myogenesis. Normally, they remain in a quiescent state until activated by a stimulus, after which they proliferate, differentiate, and fuse into an existing myofiber or form a de novo myofiber. To study satellite cell dynamics in adult murine models, most studies utilize regeneration models in which the muscle is severely damaged and requires the participation from satellite cells in order to repair. Here, we describe a model to study satellite cell behavior in muscle hypertrophy that is independent of muscle regeneration.Synergist ablation surgery involves the surgical removal of the gastrocnemius and soleus muscles resulting in functional overload of the remaining plantaris muscle. This functional overload results in myofiber hypertrophy, as well as the activation, proliferation, and fusion of satellite cells into the myofibers. Within 2 weeks of functional overload, satellite cell content increases approximately 275 %, an increase that is accompanied with a ~60 % increase in the number of myonuclei. Therefore, this can be used as an alternative model to study satellite cell behavior in adulthood that is different from regeneration, and capable of revealing new satellite cell functions in regulating muscle adaptation. PMID:27492164

  2. Synergist Ablation as a Rodent Model to Study Satellite Cell Dynamics in Adult Skeletal Muscle.

    PubMed

    Kirby, Tyler J; McCarthy, John J; Peterson, Charlotte A; Fry, Christopher S

    2016-01-01

    In adult skeletal muscles, satellite cells are the primary myogenic stem cells involved in myogenesis. Normally, they remain in a quiescent state until activated by a stimulus, after which they proliferate, differentiate, and fuse into an existing myofiber or form a de novo myofiber. To study satellite cell dynamics in adult murine models, most studies utilize regeneration models in which the muscle is severely damaged and requires the participation from satellite cells in order to repair. Here, we describe a model to study satellite cell behavior in muscle hypertrophy that is independent of muscle regeneration.Synergist ablation surgery involves the surgical removal of the gastrocnemius and soleus muscles resulting in functional overload of the remaining plantaris muscle. This functional overload results in myofiber hypertrophy, as well as the activation, proliferation, and fusion of satellite cells into the myofibers. Within 2 weeks of functional overload, satellite cell content increases approximately 275 %, an increase that is accompanied with a ~60 % increase in the number of myonuclei. Therefore, this can be used as an alternative model to study satellite cell behavior in adulthood that is different from regeneration, and capable of revealing new satellite cell functions in regulating muscle adaptation.

  3. An integrated muscle mechanic-fluid dynamic model of lamprey swimming

    NASA Astrophysics Data System (ADS)

    Hsu, Chia-Yu; Tytell, Eric; Fauci, Lisa

    2009-11-01

    In an effort towards a detailed understanding of the generation and control of vertebrate locomotion, including the role of the CPG and its interactions with reflexive feedback, muscle mechanics, and external fluid dynamics, we study a simple vertebrate, the lamprey. Lamprey body undulations are a result of a wave of neural activation that passes from head to tail, causing a wave of muscle activation. These active forces are mediated by passive structural forces. We present recent results from a model that fully couples a viscous, incompressible fluid with nonlinear muscle mechanics. We measure the dependence of the phase lag between activation wave and mechanical wave as a function of model parameters, such as body stiffness and muscle strength. Simulation results are compared to experiments utilizing both real and synthetic lamprey.

  4. Hindlimb musculature of the largest living rodent Hydrochoerus hydrochaeris (Caviomorpha): Adaptations to semiaquatic and terrestrial styles of life.

    PubMed

    García-Esponda, César M; Candela, Adriana M

    2016-03-01

    The caviomorph species Hydrochoerus hydrochaeris (Cavioidea), or capybara, is the largest living rodent. This species is widely distributed, from northern South America to Uruguay and eastern Argentina, inhabiting in a wide variety of densely vegetated lowlands habitats in the proximity of water. Hydrochoerus hydrochaeris not only runs with agility, like other members of the Cavioidea, but it can also swim and dive easily. For these reasons, it has been classified as a cursorial as well as semiaquatic species. However, comprehensive anatomical descriptions of the osteology and myology of the capybara are not available in the literature and analyses on its swimming abilities are still required. We hypothesize that some of the characters of the hindlimb of H. hydrochaeris could reveal a unique morphological arrangement associated with swimming abilities. In this study, an anatomical description of the hindlimb musculature of H. hydrochaeris, and a discussion of the possible functional significance of the main muscles is provided. In addition, we explore the evolution of some myological and osteological characters of the capybara in the context of the cavioids. We concluded that most of the muscular and osteological features of the hindlimb of H. hydrochaeris are neither adaptations to a specialized cursoriality, nor major modifications for an aquatic mode of life. Hydrochoerus hydrochaeris share several features with other cavioids, being a generalized cursorial species in the context of this clade. However, it shows some adaptations of the hindlimb for enhancing propulsion through water, of which the most notable seems to be the shortening of the leg, short tendons of most muscles of the leg, and a well-developed soleus muscle. These adaptations to a semiaquatic mode of life could have been acquired during the most recent evolutionary history of the hydrochoerids.

  5. The effect of tendon on muscle force in dynamic isometric contractions: a simulation study.

    PubMed

    van Soest, A J; Huijing, P A; Solomonow, M

    1995-07-01

    Recently, Baratta and Solomonow J. Biomechanics 24, 109-116 (1991) studied the effect of tendon on muscle-tendon complex behavior in cat tibialis anterior (TA) muscle. This was done by determining the relation between neural stimulation and muscle force in a dynamic isometric experiment, both before and after the removal of the distal tendon. From their results, Baratta and Solomonow concluded that in isometric and concentric contractions at mid-range force levels, tendon behaves as a rigid force conductor. This conclusion is in conflict with literature in which several functions are attributed to the elastic behavior of the series elastic element (SEE), of which tendon is the major part. The present study investigates the expected generalizability of their findings, by simulating the experiments using a straightforward Hill-type muscle model. First, model predictions are shown to be in line with the experimental results on cat TA: in dynamic isometric experiments at mid-range force levels, the effect of SEE removal is indeed negligible. Second, the effect of SEE removal is predicted to vary largely among muscles. Third, the most important determinants of the effect of SEE removal in dynamic isometric contractions are shown to be maximum fiber shortening velocity and the ratio of SEE slack length to fibre optimum length. PMID:7657678

  6. Hindlimb unloading of growing rats: a model for predicting skeletal changes during space flight

    NASA Technical Reports Server (NTRS)

    Morey-Holton, E. R.; Globus, R. K.

    1998-01-01

    A model that uses hindlimb unloading of rats was developed to study the consequences of skeletal unloading and reloading as occurs during and following space flight. Studies using the model were initiated two decades ago and further developed at National Aeronautics and Space Administration (NASA)-Ames Research Center. The model mimics some aspects of exposure to microgravity by removing weightbearing loads from the hindquarters and producing a cephalic fluid shift. Unlike space flight, the forelimbs remain loaded in the model, providing a useful internal control to distinguish between the local and systemic effects of hindlimb unloading. Rats that are hindlimb unloaded by tail traction gain weight at the same rate as pairfed controls, and glucocorticoid levels are not different from controls, suggesting that systemic stress is minimal. Unloaded bones display reductions in cancellous osteoblast number, cancellous mineral apposition rate, trabecular bone volume, cortical periosteal mineralization rate, total bone mass, calcium content, and maturation of bone mineral relative to controls. Subsequent studies reveal that these changes also occur in rats exposed to space flight. In hindlimb unloaded rats, bone formation rates and masses of unloaded bones decline relative to controls, while loaded bones do not change despite a transient reduction in serum 1,25-dihydroxyvitamin D (1,25D) concentrations. Studies using the model to evaluate potential countermeasures show that 1,25D, growth hormone, dietary calcium, alendronate, and muscle stimulation modify, but do not completely correct, the suppression of bone growth caused by unloading, whereas continuous infusion of transforming growth factor-beta2 or insulin-like growth factor-1 appears to protect against some of the bone changes caused by unloading. These results emphasize the importance of local as opposed to systemic factors in the skeletal response to unloading, and reveal the pivotal role that osteoblasts play in

  7. Estimation of skeletal muscle interstitial adenosine during forearm dynamic exercise in humans

    NASA Technical Reports Server (NTRS)

    Costa, F.; Heusinkveld, J.; Ballog, R.; Davis, S.; Biaggioni, I.

    2000-01-01

    It has been proposed that adenosine is a metabolic signal that triggers activation of muscle afferents involved in the exercise pressor reflex. Furthermore, exogenous adenosine induces sympathetic activation that mimics the exercise pressor reflex, and blockade of adenosine receptors inhibits sympathetic activation induced by exercise. Thus, we hypothesize that adenosine is released locally by the muscle during exercise. We used microdialysis probes, placed in the flexor digitorium superficialis muscle, to estimate muscle interstitial adenosine levels in humans. We estimated resting in vivo muscle interstitial adenosine concentrations (0.292+/-0.058 micromol/L, n=4) by perfusing increasing concentrations of adenosine to determine the gradient produced in the dialysate. Muscle interstitial adenosine concentrations increased from 0.23+/-0.04 to 0.82+/-0.14 micromol/L (n=14, P<0.001) during intermittent dynamic exercise at 50% of maximal voluntary contraction. Lactate increased from 0.8+/-0.1 to 2.3+/-0.3 mmol/L (P<0.001). Lower intensity (15% maximal voluntary contraction) intermittent dynamic exercise increased adenosine concentrations from 0.104+/-0.02 to 0.42+/-0.16 micromol/L (n=7). The addition of ischemia to this low level of exercise produced a greater increase in adenosine (from 0.095+/-0.02 to 0.48+/-0.2 micromol/L) compared with nonischemic exercise (0. 095+/-0.02 to 0.25+/-0.12 micromol/L). These results indicate that microdialysis is useful in estimating adenosine concentrations and in reflecting changes in muscle interstitial adenosine during dynamic exercise in humans.

  8. An attempt to bridge muscle architecture dynamics and its instantaneous rate of force development using ultrasonography.

    PubMed

    Li, Jizhou; Zhou, Yongjin; Zheng, Yong-Ping; Li, Guanglin

    2015-08-01

    Muscle force output is an essential index in rehabilitation assessment or physical exams, and could provide considerable insights for various applications such as load monitoring and muscle assessment in sports science or rehabilitation therapy. Besides direct measurement of force output using a dynamometer, electromyography has earlier been used in several studies to quantify muscle force as an indirect means. However, its spatial resolution is easily compromised as a summation of the action potentials from neighboring motor units of electrode site. To explore an alternative method to indirectly estimate the muscle force output, and with better muscle specificity, we started with an investigation on the relationship between architecture dynamics and force output of triceps surae. The muscular architecture dynamics is captured in ultrasonography sequences and estimated using a previously reported motion estimation method. Then an indicator named as the dorsoventrally averaged motion profile (DAMP) is employed. The performance of force output is represented by an instantaneous version of the rate of force development (RFD), namely I-RFD. From experimental results on ten normal subjects, there were significant correlations between the I-RFD and DAMP for triceps surae, both normalized between 0 and 1, with the sum of squares error at 0.0516±0.0224, R-square at 0.7929±0.0931 and root mean squared error at 0.0159±0.0033. The statistical significance results were less than 0.01. The present study suggested that muscle architecture dynamics extracted from ultrasonography during contraction is well correlated to the I-RFD and it can be a promising option for indirect estimation of muscle force output.

  9. Effect of hindlimb unweighting on tissue blood flow in the rat

    NASA Technical Reports Server (NTRS)

    Mcdonald, K. S.; Delp, M. D.; Fitts, R. H.

    1992-01-01

    This study characterized distribution of blood flow in the rat during hindlimb unweighting (HU), and post-HU standing and exercise. The relationship between reduced hindlimb blood flow and the previously observed elevation in anaerobic metabolism observed with contractile activity in the atrophied soleus muscle was examined (Witzmann et al., 1992). Blood flow was measured during unweighting, normal standing, and running on a treadmill (15 m/min), after 15 days of HU or cage control. For another group blood flow was measured during preexercise treadmill standing and treadmill running. During unweighting, PE standing, and running no difference in soleus blood flow was observed between groups. Muscles composed mainly of fast twitch glycolytic fibers received greater blood flow during chronic unweighting. With exercise blood flow to visceral organs was reduced in control animals, a similar change was not seen in 15 day HU rats. These changes suggest a reduction in the ability of the sympathetic nervous system to distribute cardiac output after chronic HU. A reduction in blood flow to the soleus during exercise was not observed after HU and so does not explain the increased dependence of the atrophied soleus on anerobic energy production during contractile activity.

  10. Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads

    PubMed Central

    Bazrgari, Babak; Arjmand, Navid

    2006-01-01

    Despite the well-recognized role of lifting in back injuries, the relative biomechanical merits of squat versus stoop lifting remain controversial. In vivo kinematics measurements and model studies are combined to estimate trunk muscle forces and internal spinal loads under dynamic squat and stoop lifts with and without load in hands. Measurements were performed on healthy subjects to collect segmental rotations during lifts needed as input data in subsequent model studies. The model accounted for nonlinear properties of the ligamentous spine, wrapping of thoracic extensor muscles to take curved paths in flexion and trunk dynamic characteristics (inertia and damping) while subject to measured kinematics and gravity/external loads. A dynamic kinematics-driven approach was employed accounting for the spinal synergy by simultaneous consideration of passive structures and muscle forces under given posture and loads. Results satisfied kinematics and dynamic equilibrium conditions at all levels and directions. Net moments, muscle forces at different levels, passive (muscle or ligamentous) forces and internal compression/shear forces were larger in stoop lifts than in squat ones. These were due to significantly larger thorax, lumbar and pelvis rotations in stoop lifts. For the relatively slow lifting tasks performed in this study with the lowering and lifting phases each lasting ∼2 s, the effect of inertia and damping was not, in general, important. Moreover, posterior shift in the position of the external load in stoop lift reaching the same lever arm with respect to the S1 as that in squat lift did not influence the conclusion of this study on the merits of squat lifts over stoop ones. Results, for the tasks considered, advocate squat lifting over stoop lifting as the technique of choice in reducing net moments, muscle forces and internal spinal loads (i.e., moment, compression and shear force). PMID:17103232

  11. Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans.

    PubMed

    Ichinose, Masashi; Ichinose-Kuwahara, Tomoko; Kondo, Narihiko; Nishiyasu, Takeshi

    2015-11-15

    Reducing blood flow to working muscles during dynamic exercise causes metabolites to accumulate within the active muscles and evokes systemic pressor responses. Whether a similar cardiovascular response is elicited with normal blood flow to exercising muscles during dynamic exercise remains unknown, however. To address that issue, we tested whether cardiovascular responses are affected by increases in blood flow to active muscles. Thirteen healthy subjects performed dynamic plantarflexion exercise for 12 min at 20%, 40%, and 60% of peak workload (EX20, EX40, and EX60) with their lower thigh enclosed in a negative pressure box. Under control conditions, the box pressure was the same as the ambient air pressure. Under negative pressure conditions, beginning 3 min after the start of the exercise, the box pressure was decreased by 20, 45, and then 70 mmHg in stepwise fashion with 3-min step durations. During EX20, the negative pressure had no effect on blood flow or the cardiovascular responses measured. However, application of negative pressure increased blood flow to the exercising leg during EX40 and EX60. This increase in blood flow had no significant effect on systemic cardiovascular responses during EX40, but it markedly attenuated the pressor responses otherwise seen during EX60. These results demonstrate that during mild exercise, normal blood flow to exercising muscle is not a factor eliciting cardiovascular responses, whereas it elicits an important pressor effect during moderate exercise. This suggests blood flow to exercising muscle is a major determinant of cardiovascular responses during dynamic exercise at higher than moderate intensity.

  12. Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans.

    PubMed

    Ichinose, Masashi; Ichinose-Kuwahara, Tomoko; Kondo, Narihiko; Nishiyasu, Takeshi

    2015-11-15

    Reducing blood flow to working muscles during dynamic exercise causes metabolites to accumulate within the active muscles and evokes systemic pressor responses. Whether a similar cardiovascular response is elicited with normal blood flow to exercising muscles during dynamic exercise remains unknown, however. To address that issue, we tested whether cardiovascular responses are affected by increases in blood flow to active muscles. Thirteen healthy subjects performed dynamic plantarflexion exercise for 12 min at 20%, 40%, and 60% of peak workload (EX20, EX40, and EX60) with their lower thigh enclosed in a negative pressure box. Under control conditions, the box pressure was the same as the ambient air pressure. Under negative pressure conditions, beginning 3 min after the start of the exercise, the box pressure was decreased by 20, 45, and then 70 mmHg in stepwise fashion with 3-min step durations. During EX20, the negative pressure had no effect on blood flow or the cardiovascular responses measured. However, application of negative pressure increased blood flow to the exercising leg during EX40 and EX60. This increase in blood flow had no significant effect on systemic cardiovascular responses during EX40, but it markedly attenuated the pressor responses otherwise seen during EX60. These results demonstrate that during mild exercise, normal blood flow to exercising muscle is not a factor eliciting cardiovascular responses, whereas it elicits an important pressor effect during moderate exercise. This suggests blood flow to exercising muscle is a major determinant of cardiovascular responses during dynamic exercise at higher than moderate intensity. PMID:26377556

  13. Multivariable dynamic ankle mechanical impedance with relaxed muscles.

    PubMed

    Lee, Hyunglae; Krebs, Hermano Igo; Hogan, Neville

    2014-11-01

    Neurological or biomechanical disorders may distort ankle mechanical impedance and thereby impair locomotor function. This paper presents a quantitative characterization of multivariable ankle mechanical impedance of young healthy subjects when their muscles were relaxed, to serve as a baseline to compare with pathophysiological ankle properties of biomechanically and/or neurologically impaired patients. Measurements using a highly backdrivable wearable ankle robot combined with multi-input multi-output stochastic system identification methods enabled reliable characterization of ankle mechanical impedance in two degrees-of-freedom (DOFs) simultaneously, the sagittal and frontal planes. The characterization included important ankle properties unavailable from single DOF studies: coupling between DOFs and anisotropy as a function of frequency. Ankle impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness in both seated (knee flexed) and standing (knee straightened) postures. Stiffness in the sagittal plane was greater than in the frontal plane and furthermore, was greater when standing than when seated, most likely due to the stretch of bi-articular muscles (medial and lateral gastrocnemius). Very low off-diagonal partial coherences implied negligible coupling between dorsiflexion-plantarflexion and inversion-eversion. The directions of principal axes were tilted slightly counterclockwise from the original joint coordinates. The directional variation (anisotropy) of ankle impedance in the 2-D space formed by rotations in the sagittal and frontal planes exhibited a characteristic "peanut" shape, weak in inversion-eversion over a wide range of frequencies from the stiffness dominated region up to the inertia dominated region. Implications for the assessment of neurological and biomechanical impairments are discussed.

  14. Myotubularin controls desmin intermediate filament architecture and mitochondrial dynamics in human and mouse skeletal muscle

    PubMed Central

    Hnia, Karim; Tronchère, Helene; Tomczak, Kinga K.; Amoasii, Leonela; Schultz, Patrick; Beggs, Alan H.; Payrastre, Bernard; Mandel, Jean Louis; Laporte, Jocelyn

    2010-01-01

    Muscle contraction relies on a highly organized intracellular network of membrane organelles and cytoskeleton proteins. Among the latter are the intermediate filaments (IFs), a large family of proteins mutated in more than 30 human diseases. For example, mutations in the DES gene, which encodes the IF desmin, lead to desmin-related myopathy and cardiomyopathy. Here, we demonstrate that myotubularin (MTM1), which is mutated in individuals with X-linked centronuclear myopathy (XLCNM; also known as myotubular myopathy), is a desmin-binding protein and provide evidence for direct regulation of desmin by MTM1 in vitro and in vivo. XLCNM-causing mutations in MTM1 disrupted the MTM1-desmin complex, resulting in abnormal IF assembly and architecture in muscle cells and both mouse and human skeletal muscles. Adeno-associated virus–mediated ectopic expression of WT MTM1 in Mtm1-KO muscle reestablished normal desmin expression and localization. In addition, decreased MTM1 expression and XLCNM-causing mutations induced abnormal mitochondrial positioning, shape, dynamics, and function. We therefore conclude that MTM1 is a major regulator of both the desmin cytoskeleton and mitochondria homeostasis, specifically in skeletal muscle. Defects in IF stabilization and mitochondrial dynamics appear as common physiopathological features of centronuclear myopathies and desmin-related myopathies. PMID:21135508

  15. Muscle Oxygen Uptake Differs from Consumption Dynamics During Transients in Exercise

    PubMed Central

    Lai, Nicola; Syed, Nakisha; Saidel, Gerald M.; Cabrera, Marco E.

    2013-01-01

    Relating external to internal respiration during exercise requires quantitative modeling analysis for reliable inferences with respect to metabolic rate. Often, oxygen transport and metabolism based on steady-state mass balances (Fick principle) and passive diffusion between blood and tissue are applied to link pulmonary to cellular respiration. Indeed, when the work rate does not change rapidly, a quasi-steady-state analysis based on the Fick principle is sufficient to estimate the rate of O2 consumption in working muscle. During exercise when the work rate changes quickly, however, non-invasive in vivo measurements to estimate muscle O2 consumption are not sufficient to characterize cellular respiration of working muscle. To interpret transient changes of venous O2 concentration, blood flow, and O2 consumption in working muscle, a mathematical model of O2 transport and consumption based on dynamic mass balances is required. In this study, a comparison is made of the differences between simulations of O2 uptake and O2 consumption within working skeletal muscle based on a dynamic model and quasi-steady-state approximations. The conditions are specified under which the quasi-steady-state approximation becomes invalid. PMID:18290343

  16. Evaluation of methods for extraction of the volitional EMG in dynamic hybrid muscle activation

    PubMed Central

    Langzam, Eran; Isakov, Eli; Mizrahi, Joseph

    2006-01-01

    Background Hybrid muscle activation is a modality used for muscle force enhancement, in which muscle contraction is generated from two different excitation sources: volitional and external, by means of electrical stimulation (ES). Under hybrid activation, the overall EMG signal is the combination of the volitional and ES-induced components. In this study, we developed a computational scheme to extract the volitional EMG envelope from the overall dynamic EMG signal, to serve as an input signal for control purposes, and for evaluation of muscle forces. Methods A "synthetic" database was created from in-vivo experiments on the Tibialis Anterior of the right foot to emulate hybrid EMG signals, including the volitional and induced components. The database was used to evaluate the results obtained from six signal processing schemes, including seven different modules for filtration, rectification and ES component removal. The schemes differed from each other by their module combinations, as follows: blocking window only, comb filter only, blocking window and comb filter, blocking window and peak envelope, comb filter and peak envelope and, finally, blocking window, comb filter and peak envelope. Results and conclusion The results showed that the scheme including all the modules led to an excellent approximation of the volitional EMG envelope, as extracted from the hybrid signal, and underlined the importance of the artifact blocking window module in the process. The results of this work have direct implications on the development of hybrid muscle activation rehabilitation systems for the enhancement of weakened muscles. PMID:17123447

  17. Dynamic stability of spine using stability-based optimization and muscle spindle reflex.

    PubMed

    Zeinali-Davarani, Shahrokh; Hemami, Hooshang; Barin, Kamran; Shirazi-Adl, Aboulfazl; Parnianpour, Mohamad

    2008-02-01

    A computational method for simulation of 3-D movement of the trunk under the control of 48 anatomically oriented muscle actions was developed. Neural excitation of muscles was set based on inverse dynamics approach along with the stability-based optimization. The effect of muscle spindle reflex response on the trunk movement stability was evaluated upon the application of a perturbation moment. The method was used to simulate the trunk movement from the upright standing to 60 degrees of flexion. Incorporation of the stability condition as an additional constraint in the optimization resulted in an increase in antagonistic activities demonstrating that the antagonistic co-activation acts to increase the trunk stability in response to self-induced postural internal perturbation. In presence of a 30 Nm flexion perturbation moment, muscle spindles decreased the induced deviation of the position and velocity profiles from the desired ones. The stability-generated co-activation decreased the reflexive response of muscle spindles to the perturbation demonstrating that the rise in muscle co-activation can ameliorate the corruption of afferent neural sensory system at the expense of higher loading of the spine.

  18. Neuronal control of turtle hindlimb motor rhythms.

    PubMed

    Stein, P S G

    2005-03-01

    The turtle, Trachemys scripta elegans, uses its hindlimb during the rhythmic motor behaviors of walking, swimming, and scratching. For some tasks, one or more motor strategies or forms may be produced, e.g., forward swimming or backpaddling. This review discusses experiments that reveal characteristics of the spinal neuronal networks producing these motor behaviors. Limb-movement studies show shared properties such as rhythmic alternation between hip flexion and hip extension, as well as variable properties such as the timing of knee extension in the cycle of hip movements. Motor-pattern studies show shared properties such as rhythmic alternation between hip flexor and hip extensor motor activities, as well as variable properties such as modifiable timing of knee extensor motor activity in the cycle of hip motor activity. Motor patterns also display variations such as the hip-extensor deletion of rostral scratching. Neuronal-network studies reveal mechanisms responsible for movement and motor-pattern properties. Some interneurons in the spinal cord have shared activities, e.g., each unit is active during more than one behavior, and have distinct characteristics, e.g., each unit is most excited during a specific behavior. Interneuronal recordings during variations support the concept of modular organization of central pattern generators in the spinal cord.

  19. The effects of thermogenic agents on hindlimb oxygen consumption in the dog: ICI D7114 and noradrenaline.

    PubMed

    Gainer, J L; Briscoe, M G; Holloway, B R

    1993-01-15

    The thermogenic action of beta-adrenoceptor agonists may be due, in part, to increased metabolism in skeletal muscle. Previous results suggest that vasoconstriction is also necessary, and that the effect can be blocked by vasodilators. Both noradrenaline and the beta-3 agonist, ICI D7114, were studied using two dog hindlimb protocols. During constant perfusion conditions, ICI D7114 caused a significant increase in hindlimb oxygen consumption although it is a vasodilator. Noradrenaline resulted in a smaller rise in oxygen consumption, and produced a marked vasoconstriction. Both noradrenaline and ICI D7114 resulted in decreased oxygen consumption when the blood flow was allowed to vary in response to the drug treatment. The results suggest that changes in tissue oxygen consumption caused by beta-agonists are not related to vasomotion. PMID:8094057

  20. An evaluation of the reliability of muscle fiber cross-sectional area and fiber number measurements in rat skeletal muscle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background: The reliability of estimating muscle fiber cross-sectional area (measure of muscle fiber size) and fiber number from only a subset of fibers in rat hindlimb muscle cross-sections has not been systematically evaluated. This study examined the variability in mean estimates of fiber cross-s...

  1. Effects of pelvic stabilization on lumbar muscle activity during dynamic exercise.

    PubMed

    San Juan, Jun G; Yaggie, James A; Levy, Susan S; Mooney, Vert; Udermann, Brian E; Mayer, John M

    2005-11-01

    Many commonly utilized low-back exercise devices offer mechanisms to stabilize the pelvis and to isolate the lumbar spine, but the value of these mechanisms remains unclear. The purpose of this study was to examine the effect of pelvic stabilization on the activity of the lumbar and hip extensor muscles during dynamic back extension exercise. Fifteen volunteers in good general health performed dynamic extension exercise in a seated upright position on a lumbar extension machine with and without pelvic stabilization. During exercise, surface electromyographic activity of the lumbar multifidus and biceps femoris was recorded. The activity of the multifidus was 51% greater during the stabilized condition, whereas there was no difference in the activity of the biceps femoris between conditions. This study demonstrates that pelvic stabilization enhances lumbar muscle recruitment during dynamic exercise on machines. Exercise specialists can use these data when designing exercise programs to develop low back strength.

  2. Thermal effects on motor control and in vitro muscle dynamics of the ballistic tongue apparatus in chameleons.

    PubMed

    Anderson, Christopher V; Deban, Stephen M

    2012-12-15

    Temperature strongly affects whole-organism performance through its effect on muscle contractile rate properties, but movements powered by elastic recoil are liberated from much of the performance decline experienced by muscle-powered movements at low temperature. We examined the motor control and muscle contractile physiology underlying an elastically powered movement - tongue projection in chameleons - and the associated muscle powered retraction to test the premise that the thermal dependence of muscle contractile dynamics is conserved. We further tested the associated hypothesis that motor control patterns and muscle contractile dynamics must change as body temperature varies, despite the thermal robustness of tongue-projection performance. We found that, over 14-26°C, the latency between the onset of the tongue projector muscle activity and tongue projection was significantly affected by temperature (Q(10) of 2.56), as were dynamic contractile properties of the tongue projector and retractor muscles (Q(10) of 1.48-5.72), supporting our hypothesis that contractile rates slow with decreasing temperature and, as a result, activity durations of the projector muscle increase at low temperatures. Over 24-36°C, thermal effects on motor control and muscle contractile properties declined, indicating that temperature effects are more extreme across lower temperature ranges. Over the entire 14-36°C range, intensity of muscle activity for the tongue muscles was not affected by temperature, indicating that recruitment of motor units in neither muscle increases with decreasing temperature to compensate for declining contractile rates. These results reveal that specializations in morphology and motor control, not muscle contractile physiology, are responsible for the thermal robustness of tongue projection in chameleons.

  3. Unsteady locomotion: integrating muscle function with whole body dynamics and neuromuscular control.

    PubMed

    Biewener, Andrew A; Daley, Monica A

    2007-09-01

    By integrating studies of muscle function with analysis of whole body and limb dynamics, broader appreciation of neuromuscular function can be achieved. Ultimately, such studies need to address non-steady locomotor behaviors relevant to animals in their natural environments. When animals move slowly they likely rely on voluntary coordination of movement involving higher brain centers. However, when moving fast, their movements depend more strongly on responses controlled at more local levels. Our focus here is on control of fast-running locomotion. A key observation emerging from studies of steady level locomotion is that simple spring-mass dynamics, which help to economize energy expenditure, also apply to stabilization of unsteady running. Spring-mass dynamics apply to conditions that involve lateral impulsive perturbations, sudden changes in terrain height, and sudden changes in substrate stiffness or damping. Experimental investigation of unsteady locomotion is challenging, however, due to the variability inherent in such behaviors. Another emerging principle is that initial conditions associated with postural changes following a perturbation define different context-dependent stabilization responses. Distinct stabilization modes following a perturbation likely result from proximo-distal differences in limb muscle architecture, function and control strategy. Proximal muscles may be less sensitive to sudden perturbations and appear to operate, in such circumstances, under feed-forward control. In contrast, multiarticular distal muscles operate, via their tendons, to distribute energy among limb joints in a manner that also depends on the initial conditions of limb contact with the ground. Intrinsic properties of these distal muscle-tendon elements, in combination with limb and body dynamics, appear to provide rapid initial stabilizing mechanisms that are often consistent with spring-mass dynamics. These intrinsic mechanisms likely help to simplify the neural

  4. Forms of forward quadrupedal locomotion. I. A comparison of posture, hindlimb kinematics, and motor patterns for normal and crouched walking.

    PubMed

    Trank, T V; Chen, C; Smith, J L

    1996-10-01

    1. Posture, hindlimb kinematics, and activity patterns of selected hindlimb muscles were compared for normal and crouched treadmill walking (0.5-0.6 m/s) for eight cats. To elicit crouched walking in which the trunk and head were lowered, cats were encouraged to walk under a light-weight Plexiglas ceiling suspended 17-20 cm above the treadmill belt. Kinematic data were obtained from high-speed ciné film, and electromyograms (EMGs)-synchronized with the kinematic records-were taken from 11 hindlimb muscles. 2. The postures for the two forms of walking were distinctly different. During crouched walking, each cat lowered its entire body keeping its trunk horizontal to the treadmill belt. Also the head was lowered, with the top of the head in line with the dorsal surface of the trunk. Hip height, used as a measure for hindlimb crouch, was reduced by 30%, from an average height of 23 cm to an average height of 16 cm above the belt during the entire step cycle. 3. Average cycle periods (766 +/- 30 ms, mean +/- SD) and percentage of time devoted to swing (30%) and stance (70%) were similar for normal and crouched walking. The profiles of the hindlimb kinematics were also similar for the hip, knee, ankle, and metatarsophalangeal (MTP) joints during the step cycle, but the timing of some of the motion reversal, as well as the ranges of motion during various phases, were different at some joints for the two forms of walking. 4. During the swing phase, the transition between the flexion and extension (F-E1 reversal) occurred later in the normalized swing phase at the hip, knee, and ankle joints, and the range of flexion was increased at each joint. With greater flexion at these joints, the anatomic axis of the hindlimb (measured from hip joint to toe) was decreased and the hind paw advanced in the narrow space between the abdomen and treadmill belt. At contact, the position of the paw was less anterior to the perpendicular reference line (hip joint marker to belt) and all

  5. Effects of a multichannel dynamic functional electrical stimulation system on hemiplegic gait and muscle forces.

    PubMed

    Qian, Jing-Guang; Rong, Ke; Qian, Zhenyun; Wen, Chen; Zhang, Songning

    2015-11-01

    [Purpose] The purpose of the study was to design and implement a multichannel dynamic functional electrical stimulation system and investigate acute effects of functional electrical stimulation of the tibialis anterior and rectus femoris on ankle and knee sagittal-plane kinematics and related muscle forces of hemiplegic gait. [Subjects and Methods] A multichannel dynamic electrical stimulation system was developed with 8-channel low frequency current generators. Eight male hemiplegic patients were trained for 4 weeks with electric stimulation of the tibia anterior and rectus femoris muscles during walking, which was coupled with active contraction. Kinematic data were collected, and muscle forces of the tibialis anterior and rectus femoris of the affected limbs were analyzed using a musculoskelatal modeling approach before and after training. A paired sample t-test was used to detect the differences between before and after training. [Results] The step length of the affected limb significantly increased after the stimulation was applied. The maximum dorsiflexion angle and maximum knee flexion angle of the affected limb were both increased significantly during stimulation. The maximum muscle forces of both the tibia anterior and rectus femoris increased significantly during stimulation compared with before functional electrical stimulation was applied. [Conclusion] This study established a functional electrical stimulation strategy based on hemiplegic gait analysis and musculoskeletal modeling. The multichannel functional electrical stimulation system successfully corrected foot drop and altered circumduction hemiplegic gait pattern.

  6. Asymmetric Bilayer Muscles: Cooperative Actuation, Dynamic Hysteresis, and Creeping in NaPF6 Aqueous Solutions.

    PubMed

    Fuchiwaki, Masaki; Martinez, Jose G; Fernandez Otero, Toribio

    2016-08-01

    Three bilayer muscles [polypyrrole-paraphenolsulfonic acid/polypyrrole-dodecylbenzensulfonic acid (PPy-HpPS/PPy-DBS) asymmetric bilayer, PPy-HpPS/tape, and PPy-DBS/tape] were characterized during potential cycling in NaPF6 aqueous solutions. In parallel, the angular displacement of the muscle was video-recorded. The dynamo-voltammetric (angle-potential) and coulo-dynamic (charge-potential) results give the reaction-driven ionic exchanges in each PPy film. Electrochemical reactions drive the exchange of anions from the PPy-HpPS layer and cations from the PPy-DBS layer. This means that both layers from the asymmetric bilayer follow complementary volume changes (swelling/shrinking or shrinking/swelling), owing to complementary ionic exchanges (entrance/expulsion) driven by the bilayer oxidation or reduction. The result is a cooperative actuation; the bending amplitude described by the asymmetric bilayer muscle is one order of magnitude larger than those attained from each of the conducting polymer/tape muscles. The cooperative actuation almost eliminates creeping effects. A large dynamical hysteresis persists, which can be attributed to an irreversible reaction of the organic acid components at high overpotentials. PMID:27547647

  7. Asymmetric Bilayer Muscles: Cooperative Actuation, Dynamic Hysteresis, and Creeping in NaPF6 Aqueous Solutions.

    PubMed

    Fuchiwaki, Masaki; Martinez, Jose G; Fernandez Otero, Toribio

    2016-08-01

    Three bilayer muscles [polypyrrole-paraphenolsulfonic acid/polypyrrole-dodecylbenzensulfonic acid (PPy-HpPS/PPy-DBS) asymmetric bilayer, PPy-HpPS/tape, and PPy-DBS/tape] were characterized during potential cycling in NaPF6 aqueous solutions. In parallel, the angular displacement of the muscle was video-recorded. The dynamo-voltammetric (angle-potential) and coulo-dynamic (charge-potential) results give the reaction-driven ionic exchanges in each PPy film. Electrochemical reactions drive the exchange of anions from the PPy-HpPS layer and cations from the PPy-DBS layer. This means that both layers from the asymmetric bilayer follow complementary volume changes (swelling/shrinking or shrinking/swelling), owing to complementary ionic exchanges (entrance/expulsion) driven by the bilayer oxidation or reduction. The result is a cooperative actuation; the bending amplitude described by the asymmetric bilayer muscle is one order of magnitude larger than those attained from each of the conducting polymer/tape muscles. The cooperative actuation almost eliminates creeping effects. A large dynamical hysteresis persists, which can be attributed to an irreversible reaction of the organic acid components at high overpotentials.

  8. Asymmetric Bilayer Muscles: Cooperative Actuation, Dynamic Hysteresis, and Creeping in NaPF6 Aqueous Solutions

    PubMed Central

    Fuchiwaki, Masaki; Martinez, Jose G.

    2016-01-01

    Abstract Three bilayer muscles [polypyrrole–paraphenolsulfonic acid/polypyrrole–dodecylbenzensulfonic acid (PPy–HpPS/PPy–DBS) asymmetric bilayer, PPy–HpPS/tape, and PPy–DBS/tape] were characterized during potential cycling in NaPF6 aqueous solutions. In parallel, the angular displacement of the muscle was video‐recorded. The dynamo‐voltammetric (angle–potential) and coulo‐dynamic (charge–potential) results give the reaction‐driven ionic exchanges in each PPy film. Electrochemical reactions drive the exchange of anions from the PPy–HpPS layer and cations from the PPy–DBS layer. This means that both layers from the asymmetric bilayer follow complementary volume changes (swelling/shrinking or shrinking/swelling), owing to complementary ionic exchanges (entrance/expulsion) driven by the bilayer oxidation or reduction. The result is a cooperative actuation; the bending amplitude described by the asymmetric bilayer muscle is one order of magnitude larger than those attained from each of the conducting polymer/tape muscles. The cooperative actuation almost eliminates creeping effects. A large dynamical hysteresis persists, which can be attributed to an irreversible reaction of the organic acid components at high overpotentials. PMID:27547647

  9. A Magnetic Resonance-Compatible Loading Device for Dynamically Imaging Shortening and Lengthening Muscle Contraction Mechanics

    PubMed Central

    Silder, Amy; Westphal, Christopher J.; Thelen, Darryl G.

    2013-01-01

    The purpose of this study was to design and test a magnetic resonance (MR)-compatible device to induce either shortening or lengthening muscle contractions for use during dynamic MR imaging. The proposed device guides the knee through cyclic flexion-extension, while either elastic or inertial loads are imposed on the hamstrings. Ten subjects were tested in a motion capture laboratory to evaluate the repeatability of limb motion and imposed loads. Image data were subsequently obtained for all ten subjects using cine phase contrast imaging. Subjects achieved ~30 deg of knee joint motion, with individual subjects remaining within ~1 deg of their average motion across 56 repeated cycles. The maximum hamstring activity and loading occurred when the knee was flexed for the elastic loading condition (shortening contraction), and extended for the inertial loading condition (lengthening contraction). Repeat MR image acquisitions of the same loading condition resulted in similar tissue velocities, while spatial variations in velocity data were clearly different between loading conditions. The proposed device can enable dynamic imaging of the muscle under different types of loads, which has the potential to improve our understanding of basic muscle mechanics, identify potential causes of muscle injury, and provide a basis for quantitatively assessing injury effects at the tissue level. Slight modifications to the device design and/or subject positioning could allow for imaging of the quadriceps or the knee. PMID:24353749

  10. Time course of vasodilatory responses in skeletal muscle arterioles: role in hyperemia at onset of exercise

    NASA Technical Reports Server (NTRS)

    Wunsch, S. A.; Muller-Delp, J.; Delp, M. D.

    2000-01-01

    At the onset of dynamic exercise, muscle blood flow increases within 1-2 s. It has been postulated that local vasodilatory agents produced by the vascular endothelium or the muscle itself contribute to this response. We hypothesized that only vasodilators that act directly on the vascular smooth muscle could produce vasodilation of skeletal muscle arterioles in <2 s. To test this hypothesis, we determined the time course of the vasodilatory response of isolated skeletal muscle arterioles to direct application of potassium chloride, adenosine, acetylcholine, and sodium nitroprusside. Soleus and gastrocnemius muscles were dissected from the hindlimbs of male Sprague-Dawley rats. First-order arterioles (100-200 microm) were isolated, cannulated on micropipettes, and pressurized to 60 cmH(2)O in an organ bath. Vasodilatory agents were added directly to the bath, and diameter responses of the arterioles were recorded in real time on a videotape recorder. Frame-by-frame analysis of the diameter responses indicated that none of the vasodilator agents tested produced significant diameter increases in <4 s in either soleus or gastrocnemius muscle arterioles. These results indicate that, although these local vasodilators produce significant vasodilation of skeletal muscle resistance arterioles, these responses are not rapid enough (within 1-2 s) to contribute to the initiation of the exercise hyperemic response at the onset of dynamic exercise.

  11. Fatigability and Blood Flow in the Rat Gastrocnemius-Plantaris-Soleus after Hindlimb Suspension

    NASA Technical Reports Server (NTRS)

    McDonald, K. S.; Delp, M. D.; Fitts, R. H.

    1992-01-01

    The purpose of this study was to test the hypothesis that hindlimb suspension increases the fatigability of the soleus during intense contractile activity and determine whether the increased fatigue is associated with a reduced muscle blood flow. Cage-control (C) and 15-day hindlimb-suspended (HS) rats were anesthetized, and either the gastrocnemius-plantaris-soleus (G-P-S) muscle group or the soleus was stimulated (100 Hz, 100-ms trains at 120/min) for 10 min in situ. In the G-P-S preparation, blood flow was measured with radiolabeled microspheres before and at 2 and 10 min of contractile activity. The G-P-S fatigued markedly at this stimulation frequency, and the differences between C and HS animals were not significant until the 9th min of contractile activity. In contrast, the stimulation resulted in faster rates and significantly larger amounts of fatigue in the soleus from HS than from C animals. The atrophied soleus showed significant differences by I min of stimulation (C = 70 +/- 1% vs. HS = 57 +/- 2% of peak train force) and remained different at 10 min (C = 64 +/- 4% vs. HS = 45 +/- 2% peak train force). Relative blood flow to the soleus was similar between groups before and during contractile activity (rest: C = 20 +/- 3 vs. HS= 12 +/- 3; 2 min: C= 128 +/- 6 vs. HS = 118 +/- 4; 10 min: C = 123 +/- 11 vs. HS = 105 +/- 11 ml min(exp -1) 100 g(exp -1)). In conclusion, these results established that 15 days of HS increased the fatigability of the soleus, but the effect was not caused by a reduced muscle blood flow.

  12. Hindlimb Motor Neurons Require Cu/Zn Superoxide Dismutase for Maintenance of Neuromuscular Junctions

    PubMed Central

    Flood, Dorothy G.; Reaume, Andrew G.; Gruner, John A.; Hoffman, Eric K.; Hirsch, James D.; Lin, Yin-Guo; Dorfman, Karen S.; Scott, Richard W.

    1999-01-01

    The role of oxidative damage in neurodegenerative disease was investigated in mice lacking cytoplasmic Cu/Zn superoxide dismutase (SOD), created by deletion of the SOD1 gene (SOD1−/−). SOD1−/− mice developed a chronic peripheral hindlimb axonopathy. Mild denervation of muscle was detected at 2 months, and behavioral and physiological motor deficits were present at 5–7 months of age. Ventral root axons were shrunken but were normal in number. The somatosensory system in SOD1−/− mice was mildly affected. SOD1−/− mice expressing Cu/Zn SOD only in brain and spinal cord were generated using transgenic mice expressing mouse SOD1 driven by the neuron-specific synapsin promoter. Neuron-specific expression of Cu/Zn SOD in SOD1−/− mice rescued motor neurons from the neuropathy. Therefore, Cu/Zn SOD is not required for normal motor neuron survival, but is necessary for the maintenance of normal neuromuscular junctions by hindlimb motor neurons. PMID:10433959

  13. Umbilical Cord-Derived Mesenchymal Stem Cells Relieve Hindlimb Ischemia through Enhancing Angiogenesis in Tree Shrews

    PubMed Central

    Yin, Cunping; Liang, Yuan; Zhang, Jian; Li, Zian; Pang, Rongqing

    2016-01-01

    Hindlimb ischemia is still a clinical problem with high morbidity and mortality. Patients suffer from consequent rest pain, ulcers, cool limbs, and even amputation. Angiogenesis is a promising target for the treatment of ischemic limbs, providing extra blood for the ischemic region. In the present study, we investigated the role of umbilical cord-derived mesenchymal stem cells (UC-MSCs) in regulating angiogenesis and relieving hindlimb ischemia. UC-MSCs were isolated from the umbilical cord of tree shrews. Angiography results showed that UC-MSCs injection significantly promoted angiogenesis in tree shrews. Moreover, the ankle brachial index, transcutaneous oxygen pressure, blood perfusion, and capillary/muscle fiber ratio were all markedly increased by the application of UC-MSCs. In addition, the conditioned culture of human umbilical vein endothelial cells using medium collected from UC-MSCs showed higher expression of angiogenic markers and improved migration ability. In short, the isolated UC-MSCs notably contributed to restoring blood supply and alleviating the symptoms of limb ischemia through enhancing angiogenesis. PMID:27651800

  14. Effects of Spaceflight and Hindlimb Suspension on the Posture and Gait of Rats

    NASA Technical Reports Server (NTRS)

    Fox, R. A.; Corcoran, M.; Daunton, N. G.; Morey-Holton, E.

    1994-01-01

    Instability of posture and gait in astronauts following spaceflight (SF) is thought to result from muscle atrophy and from changes in sensory-motor integration in the CNS (central nervous system) that occur during adaptation to microgravity (micro-G). Individuals are thought to have developed, during SF, adaptive changes for the processing of proprioceptive, vestibular and visual sensory inputs with reduced weighting of gravity-based signals and increased weighting of visual and tactile cues. This sensory-motor rearrangement in the CNS apparently occurs to optimize neuromuscular system function for effective movement and postural control in micro-G. However, these adaptive changes are inappropriate for the 1 g environment and lead to disruptions in posture and gait on return to Earth. Few reports are available on the effects of SF on the motor behavior of animals. Rats studied following 18.5 - 19.5 days of SF in the COSMOS program were described as being ..'inert, apathetic, slow'.. and generally unstable. The hindlimbs of these rats were ..'thrust out from the body with fingers pulled apart and the shin unnaturally pronated'. On the 6th postflight day motor behavior was described as similar to that observed in preflight observations. Improved understanding of the mechanisms leading to these changes can be obtained in animal models through detailed analysis of neural and molecular mechanisms related to gait. To begin this process the posture and gait of rats were examined following exposure to either SF or hindlimb suspension (HLS), and during recovery from these conditions.

  15. Maximal vasodilation does not eliminate the vascular waterfall in the canine hindlimb.

    PubMed

    Shrier, I; Magder, S

    1995-11-01

    Previous studies have shown that blood flow through skeletal muscle is regulated by changes in an arteriolar vascular waterfall [critical pressure (Pcrit)] and a proximal (arterial) resistance (Ra) element. To determine whether Pcrit still exists during maximal vasodilation, we pump perfused vascularly isolated canine hindlimbs. We set outflow pressure to zero and measured Pcrit, perfusion pressure (Pper), and regional elastic recoil pressure (Pcl; by a stop-flow technique) and calculated both Ra and venous resistance before and after maximal vasodilation with adenosine and nitroprusside. Pcrit was 56.4 +/- 5.1 mmHg before vasodilation and decreased to 11.0 +/- 0.6 mmHg after vasodilation, which was less than the downstream pressure in the venous compliant region (Pel). Therefore, Pcrit should not have affected flow at normal Pper levels under vasodilated conditions. However, we could still measure Pcrit because our technique allowed Pel to decline and Pcrit becomes apparent once Pel < Pcrit. With vasodilation, Ra decreased to < 8.1 +/- 2.6% and Rv decreased to 41 +/- 6% of control values. In contrast to the nonvasodilated vasculature, increases in venous pressure during maximal vasodilation caused immediate increases in Pper. This also suggests that the vascular waterfall is inactive under conditions of maximal vasodilation. We conclude that a small arteriolar Pcrit is still present in the maximally vasodilated hindlimb but is less than the downstream pressure and does not affect flow under these conditions.

  16. Umbilical Cord-Derived Mesenchymal Stem Cells Relieve Hindlimb Ischemia through Enhancing Angiogenesis in Tree Shrews

    PubMed Central

    Yin, Cunping; Liang, Yuan; Zhang, Jian; Li, Zian; Pang, Rongqing

    2016-01-01

    Hindlimb ischemia is still a clinical problem with high morbidity and mortality. Patients suffer from consequent rest pain, ulcers, cool limbs, and even amputation. Angiogenesis is a promising target for the treatment of ischemic limbs, providing extra blood for the ischemic region. In the present study, we investigated the role of umbilical cord-derived mesenchymal stem cells (UC-MSCs) in regulating angiogenesis and relieving hindlimb ischemia. UC-MSCs were isolated from the umbilical cord of tree shrews. Angiography results showed that UC-MSCs injection significantly promoted angiogenesis in tree shrews. Moreover, the ankle brachial index, transcutaneous oxygen pressure, blood perfusion, and capillary/muscle fiber ratio were all markedly increased by the application of UC-MSCs. In addition, the conditioned culture of human umbilical vein endothelial cells using medium collected from UC-MSCs showed higher expression of angiogenic markers and improved migration ability. In short, the isolated UC-MSCs notably contributed to restoring blood supply and alleviating the symptoms of limb ischemia through enhancing angiogenesis.

  17. Umbilical Cord-Derived Mesenchymal Stem Cells Relieve Hindlimb Ischemia through Enhancing Angiogenesis in Tree Shrews.

    PubMed

    Yin, Cunping; Liang, Yuan; Zhang, Jian; Ruan, Guangping; Li, Zian; Pang, Rongqing; Pan, Xinghua

    2016-01-01

    Hindlimb ischemia is still a clinical problem with high morbidity and mortality. Patients suffer from consequent rest pain, ulcers, cool limbs, and even amputation. Angiogenesis is a promising target for the treatment of ischemic limbs, providing extra blood for the ischemic region. In the present study, we investigated the role of umbilical cord-derived mesenchymal stem cells (UC-MSCs) in regulating angiogenesis and relieving hindlimb ischemia. UC-MSCs were isolated from the umbilical cord of tree shrews. Angiography results showed that UC-MSCs injection significantly promoted angiogenesis in tree shrews. Moreover, the ankle brachial index, transcutaneous oxygen pressure, blood perfusion, and capillary/muscle fiber ratio were all markedly increased by the application of UC-MSCs. In addition, the conditioned culture of human umbilical vein endothelial cells using medium collected from UC-MSCs showed higher expression of angiogenic markers and improved migration ability. In short, the isolated UC-MSCs notably contributed to restoring blood supply and alleviating the symptoms of limb ischemia through enhancing angiogenesis. PMID:27651800

  18. Stimulation of NTS A1 adenosine receptors evokes counteracting effects on hindlimb vasculature.

    PubMed

    McClure, Joseph M; O'Leary, Donal S; Scislo, Tadeusz J

    2005-12-01

    Our previous studies concluded that stimulation of the nucleus of the solitary tract (NTS) A2a receptors evokes preferential hindlimb vasodilation mainly via inducing increases in preganglionic sympathetic nerve activity (pre-ASNA) directed to the adrenal medulla. This increase in pre-ASNA causes the release of epinephrine and subsequent activation of beta-adrenergic receptors that are preferentially located in the skeletal muscle vasculature. Selective activation of NTS A1 adenosine receptors evokes variable, mostly pressor effects and increases pre-ASNA, as well as lumbar sympathetic activity, which is directed to the hindlimb. These counteracting factors may have opposite effects on the hindlimb vasculature resulting in mixed vascular responses. Therefore, in chloralose-urethane-anesthetized rats, we evaluated the contribution of vasodilator versus vasoconstrictor effects of stimulation of NTS A1 receptors on the hindlimb vasculature. We compared the changes in iliac vascular conductance evoked by microinejctions into the NTS of the selective A1 receptor agonist N6-cyclopentyladenosine (330 pmol in 50 nl volume) in intact animals with the responses evoked after beta-adrenergic blockade, bilateral adrenalectomy, bilateral lumbar sympathectomy, and combined adrenalectomy + lumbar sympathectomy. In intact animals, stimulation of NTS A1 receptors evoked variable effects: increases and decreases in mean arterial pressure and iliac conductance with prevailing pressor and vasoconstrictor effects. Peripheral beta-adrenergic receptor blockade and bilateral adrenalectomy eliminated the depressor component of the responses, markedly potentiated iliac vasoconstriction, and tended to increase the pressor responses. Lumbar sympathectomy tended to decrease the pressor and vasoconstrictor responses. After bilateral adrenalectomy plus lumbar sympathectomy, a marked vasoconstriction in iliac vascular bed still persisted, suggesting that the vasoconstrictor component of the

  19. Unsteady locomotion: integrating muscle function with whole body dynamics and neuromuscular control

    PubMed Central

    Biewener, Andrew A.; Daley, Monica A.

    2009-01-01

    Summary By integrating studies of muscle function with analysis of whole body and limb dynamics, broader appreciation of neuromuscular function can be achieved. Ultimately, such studies need to address non-steady locomotor behaviors relevant to animals in their natural environments. When animals move slowly they likely rely on voluntary coordination of movement involving higher brain centers. However, when moving fast, their movements depend more strongly on responses controlled at more local levels. Our focus here is on control of fast-running locomotion. A key observation emerging from studies of steady level locomotion is that simple spring-mass dynamics, which help to economize energy expenditure, also apply to stabilization of unsteady running. Spring-mass dynamics apply to conditions that involve lateral impulsive perturbations, sudden changes in terrain height, and sudden changes in substrate stiffness or damping. Experimental investigation of unsteady locomotion is challenging, however, due to the variability inherent in such behaviors. Another emerging principle is that initial conditions associated with postural changes following a perturbation define different context-dependent stabilization responses. Distinct stabilization modes following a perturbation likely result from proximo-distal differences in limb muscle architecture, function and control strategy. Proximal muscles may be less sensitive to sudden perturbations and appear to operate, in such circumstances, under feed-forward control. In contrast, multiarticular distal muscles operate, via their tendons, to distribute energy among limb joints in a manner that also depends on the initial conditions of limb contact with the ground. Intrinsic properties of these distal muscle–tendon elements, in combination with limb and body dynamics, appear to provide rapid initial stabilizing mechanisms that are often consistent with spring-mass dynamics. These intrinsic mechanisms likely help to simplify the

  20. Muscle-fiber conduction velocity estimated from surface EMG signals during explosive dynamic contractions.

    PubMed

    Pozzo, M; Merlo, E; Farina, D; Antonutto, G; Merletti, R; Di Prampero, P E

    2004-06-01

    Muscle-fiber conduction velocity (CV) was estimated from surface electromyographic (EMG) signals during isometric contractions and during short (150-200 ms), explosive, dynamic exercises. Surface EMG signals were recorded with four linear adhesive arrays from the vastus lateralis and medialis muscles of 12 healthy subjects. Isometric contractions were at linearly increasing force from 0% to 100% of the maximum. The dynamic contractions consisted of explosive efforts of the lower limb on a sledge ergometer. For the explosive contractions, muscle-fiber CV was estimated in seven time-windows located along the ascending time interval of the force. There was a significant correlation between CV values during the isometric ramp and explosive contractions (R = 0.75). Moreover, CV estimates increased significantly from (mean +/- SD) 4.32 +/- 0.46 m/s to 4.97 +/- 0.45 m/s during the increasing-force explosive task. It was concluded that CV can be estimated reliably during dynamic tasks involving fast limb movements and that, in these contractions, it may provide important information on motor-unit control properties.

  1. A single muscle's multifunctional control potential of body dynamics for postural control and running

    PubMed Central

    Sponberg, Simon; Spence, Andrew J.; Mullens, Chris H.; Full, Robert J.

    2011-01-01

    A neuromechanical approach to control requires understanding how mechanics alters the potential of neural feedback to control body dynamics. Here, we rewrite activation of individual motor units of a behaving animal to mimic the effects of neural feedback without concomitant changes in other muscles. We target a putative control muscle in the cockroach, Blaberus discoidalis (L.), and simultaneously capture limb and body dynamics through high-speed videography and a micro-accelerometer backpack. We test four neuromechanical control hypotheses. We supported the hypothesis that mechanics linearly translates neural feedback into accelerations and rotations during static postural control. However, during running, the same neural feedback produced a nonlinear acceleration control potential restricted to the vertical plane. Using this, we reject the hypothesis from previous work that this muscle acts primarily to absorb energy from the body. The conversion of the control potential is paralleled by nonlinear changes in limb kinematics, supporting the hypothesis that significant mechanical feedback filters the graded neural feedback for running control. Finally, we insert the same neural feedback signal but at different phases in the dynamics. In this context, mechanical feedback enables turning by changing the timing and direction of the accelerations produced by the graded neural feedback. PMID:21502129

  2. Review of spaceflight and hindlimb suspension unloading induced sarcomere damage and repair

    NASA Technical Reports Server (NTRS)

    Riley, D. A.; Thompson, J. L.; Krippendorf, B. B.; Slocum, G. R.

    1995-01-01

    Hindlimb suspension unloading (HSU) and spaceflight microgravity induce atrophy of the slow adductor longus muscle fibers which, following reloading, exhibit eccentric contraction (EC)-like lesions (abnormal widening of sarcomeres with A band disruption and excessively wavy, extracted Z lines). These lesions are similar morphologically to those produced in normal muscles after strenuous eccentric exercise. It appears that atrophic muscles exhibit increased susceptibility to eccentric damage because lesions are produced during nonstressful voluntary movements upon return to weightbearing. The EC-like lesions are absent in the unweighted conditions, but appear in HSU rats 15-60 minutes after reloading and in space-flown rates about 4 hrs after landing. By 12 hours, many EC-like lesioned sarcomeres are fully covered by longitudinal patches of Z line-like material which increases in density by 48 hours, producing the so-called "Z line streaming" morphology. In this case, Z line streaming is indicative of rapid repair of damaged sarcomeres rather than the onset of sarcomere breakdown. Immunoelectron microscopy is necessary to determine the composition of this dense material. By 9 days of reloading at 1 gravity, sarcomeres have regained normal structure, except for very rare persistence of faint Z patches. The morphological data indicate that Z patches serve at least two functions: 1) to permit contractile force to be transmitted across the damaged sarcomeres and 2) to provide a scaffold upon which sarcomeres are reconstructed in an active functional muscle.

  3. Effects of virtual reality-based ankle exercise on the dynamic balance, muscle tone, and gait of stroke patients.

    PubMed

    Yom, Changho; Cho, Hwi-Young; Lee, ByoungHee

    2015-03-01

    [Purpose] The purpose of this study was to investigate the therapeutic effects of virtual reality-based ankle exercise on the dynamic balance, muscle tone, and gait ability of stroke subjects. [Subjects and Methods] Twenty persons who were in the chronic stroke subjects of this study and they were included and assigned to two groups: experimental (VRAE; Virtual Reality-based Ankle Exercise group) (n=10) and control groups (n=10). The VRAE group performed virtual environment system ankle exercise, and the control group watched a video. Both groups performed their respective interventions for 30 minutes per day, 5 times per week over a 6-week period. To confirm the effects of the intervention, dynamic balance, muscle tone, and spatiotemporal gait were evaluated. [Results] The results showed that the dynamic balance and muscle tone was significantly more improved after the intervention compared to before in the VRAE group (dynamic balance: 5.50±2.57; muscle tone: 0.90±0.39), and the improvements were more significant than those in the control (dynamic balance: 1.22±2.05; muscle tone: 0.10±0.21). Spatiotemporal gait measures were significantly more increased in the paretic limb after the intervention compared to before in the VRAE group and the improvements were more significant than those in the control group. [Conclusion] This study demonstrated that virtual reality-based ankle exercise effectively improves the dynamic balance, muscle tone, and gait ability of stroke patients.

  4. [Dynamic rehabilitation in facial paralysis with the surgical flap and temporalis muscle transposition without muscle lengthening: review and case report].

    PubMed

    Shipkov, Kh; Anastasov, Iu

    2005-01-01

    There are various surgical procedures for the reanimation of patients with long-standing facial paralysis. Temporalis muscle transfer is reliable for the reanimation of long-standing facial paralysis often employed when facial nerve reinnervation. It can be used as well for the immediate treatment of complete facial paralysis (more than 1 year) because temporalis muscle transposition does not interfere with neuronal regeneration. During the last few years the techniques employing the tendon of the temporalis muscle for the rehabilitation of the oral commissure gain increasing importance. The authors analyse the different options for reanimation after facial paralysis and report on a case of facial reanimation via temporalis muscle transfer.

  5. Bifunctional Spin Labeling of Muscle Proteins: Accurate Rotational Dynamics, Orientation, and Distance by EPR.

    PubMed

    Thompson, Andrew R; Binder, Benjamin P; McCaffrey, Jesse E; Svensson, Bengt; Thomas, David D

    2015-01-01

    While EPR allows for the characterization of protein structure and function due to its exquisite sensitivity to spin label dynamics, orientation, and distance, these measurements are often limited in sensitivity due to the use of labels that are attached via flexible monofunctional bonds, incurring additional disorder and nanosecond dynamics. In this chapter, we present methods for using a bifunctional spin label (BSL) to measure muscle protein structure and dynamics. We demonstrate that bifunctional attachment eliminates nanosecond internal rotation of the spin label, thereby allowing the accurate measurement of protein backbone rotational dynamics, including microsecond-to-millisecond motions by saturation transfer EPR. BSL also allows for accurate determination of helix orientation and disorder in mechanically and magnetically aligned systems, due to the label's stereospecific attachment. Similarly, labeling with a pair of BSL greatly enhances the resolution and accuracy of distance measurements measured by double electron-electron resonance (DEER). Finally, when BSL is applied to a protein with high helical content in an assembly with high orientational order (e.g., muscle fiber or membrane), two-probe DEER experiments can be combined with single-probe EPR experiments on an oriented sample in a process we call BEER, which has the potential for ab initio high-resolution structure determination. PMID:26477249

  6. Static vs. Dynamic Acute Stretching Effect on Quadriceps Muscle Activity during Soccer Instep Kicking.

    PubMed

    Amiri-Khorasani, Mohammadtaghi; Kellis, Eleftherios

    2013-12-18

    The purpose of this study was to compare the effects of static and dynamic stretching on quadriceps muscle activation during maximal soccer instep kicking. The kicking motion of twelve male college soccer players (body height: 174.66 ± 5.01 cm; body mass: 72.83 ± 4.83 kg; age: 18.83 ± 0.75 years) was captured using six synchronized high-speed infra-red cameras whilst electromyography (EMG) signals from vastus medialis (VM), lateralis (VL) and rectus femoris (RF) were recorded before and after static or dynamic stretching. Analysis of variance designs showed a higher increase in knee extension angular velocity (9.65% vs. -1.45%, p < 0.001), RF (37.5% vs. -8.33%, p < 0.001), VM (12% vs. -12%, p < 0.018), and VL EMG activity (20% vs. -6.67%, p < 0.001) after dynamic stretching exercises. Based on these results, it could be suggested that dynamic stretching is probably more effective in increasing quadriceps muscle activity and knee extension angular velocity during the final swing phase of a maximal soccer instep kick than static stretching.

  7. Fatigability and recovery of arm muscles with advanced age for dynamic and isometric contractions.

    PubMed

    Yoon, Tejin; Schlinder-Delap, Bonnie; Hunter, Sandra K

    2013-02-01

    This study determined whether age-related mechanisms can increase fatigue of arm muscles during maximal velocity dynamic contractions, as it occurs in the lower limb. We compared elbow flexor fatigue of young (n=10, 20.8±2.7 years) and old men (n=16, 73.8±6.1 years) during and in recovery from a dynamic and an isometric postural fatiguing task. Each task was maintained until failure while supporting a load equivalent to 20% of maximal voluntary isometric contraction (MVIC) torque. Transcranial magnetic stimulation (TMS) was used to assess supraspinal fatigue (superimposed twitch, SIT) and muscle relaxation. Time to failure was longer for the old men than for the young men for the isometric task (9.5±3.1 vs. 17.2±7.0 min, P=0.01) but similar for the dynamic task (6.3±2.4 min vs. 6.0±2.0 min, P=0.73). Initial peak rate of relaxation was slower for the old men than for the young men, and was associated with a longer time to failure for both tasks (P<0.05). Low initial power during elbow flexion was associated with the greatest difference (reduction) in time to failure between the isometric task and the dynamic task (r=-0.54, P=0.015). SIT declined after both fatigue tasks similarly with age, although the recovery of SIT was associated with MVIC recovery for the old (both sessions) but not for the young men. Biceps brachii and brachioradialis EMG activity (% MVIC) of the old men were greater than that of the young men during the dynamic fatiguing task (P<0.05), but were similar during the isometric task. Muscular mechanisms and greater relative muscle activity (EMG activity) explain the greater fatigue during the dynamic task for the old men compared with the young men in the elbow flexor muscles. Recovery of MVC torque however relies more on the recovery of supraspinal fatigue among the old men than among the young men.

  8. Adaptive control for backward quadrupedal walking VI. metatarsophalangeal joint dynamics and motor patterns of digit muscles.

    PubMed

    Trank, T V; Smith, J L

    1996-02-01

    1. We compared the dynamics of the metatarsophalangeal (MTP) joint of the cat's hind paw and the motor patterns of two short and four long muscles of the digits for two walking forms, forward (FWD) and backward (BWD). Kinematic (angular displacements) data digitized from high-speed ciné film and electromyographic (EMG) data were synchronized and assessed for bouts of treadmill walking. Kinetic data (joint forces) were calculated from kinematic and anthropometric data with the use of inverse-dynamic calculations in which the MTP joint net torque was divided into gravitational, motion-dependent, ground contact (absent for swing), and muscle torque components. Swing-phase kinetics were calculated from treadmill steps and stance-phase kinetics from overground steps in which one hind paw contacted a miniature force platform embedded in the walkway. 2. The plantar angle at the intersection of the metatarsal and phalangeal segmental lines was used to measure MTP angular displacements. During swing for both walking forms, the MTP joint flexed (F) and then extended (E); however, the F-E transition occurred at the onset of FWD swing and at the end of BWD swing. For FWD walking, the MTP joint extended at a constant velocity during most of stance as the cat's weight rotated forward over the paw. During the unweighting phase at the end of stance, the MTP joint flexed rapidly before paw lift off. For BWD walking, the MTP joint extended briefly at stance onset (similar to a yield) and then flexed at a constant velocity as the cat's weight rotated backward over the paw. At the end of stance, the MTP joint extended and then flexed slightly as the paw was unweighted before paw lift off. 3. For both forms of walking, three of the six muscles tested were recruited just before paw contact and remained active for most (75-80%) of stance for both walking forms: plantaris (PLT), flexor hallucis longus (FHL), and flexor digitorum brevis (FDB). Their recruitment contributed to the flexor

  9. Peripheral vascular responses to heat stress after hindlimb suspension

    NASA Technical Reports Server (NTRS)

    Looft-Wilson, Robin C.; Gisolfi, Carl V.

    2002-01-01

    PURPOSE: The purpose of this study was to determine whether hindlimb suspension (which simulates the effects of microgravity) results in impaired hemodynamic responses to heat stress or alterations in mesenteric small artery sympathetic nerve innervation. METHODS: Over 28 d, 16 male Sprague-Dawley rats were hindlimb-suspended, and 13 control rats were housed in the same type of cage. After the treatment, mean arterial pressure (MAP), colonic temperature (Tcol), and superior mesenteric and iliac artery resistances (using Doppler flowmetry) were measured during heat stress [exposure to 42 degrees C until the endpoint of 80 mm Hg blood pressure was reached (75 +/- 9 min); endpoint Tcore = 43.6 +/- 0.2] while rats were anesthetized (sodium pentobarbital, 50 mg x kg(-1) BW). RESULTS: Hindlimb-suspended and control rats exhibited similar increases in Tcol, MAP, and superior mesenteric artery resistance, and similar decreases in iliac resistance during heat stress (endpoint was a fall in MAP below 80 mm Hg). Tyrosine hydroxylase immunostaining indicated similar sympathetic nerve innervation in small mesenteric arteries from both groups. CONCLUSION: Hindlimb suspension does not alter the hemodynamic or thermoregulatory responses to heat stress in the anesthetized rat or mesenteric sympathetic nerve innervation, suggesting that this sympathetic pathway is intact.

  10. Stimulation of Myofibrillar Protein Synthesis in Hindlimb Suspended Rats by Resistance Exercise and Growth Hormone

    NASA Technical Reports Server (NTRS)

    Linderman, Jon K.; Whittall, Justen B.; Gosselink, Kristin L.; Wang, Tommy J.; Mukku, Venkat R.; Booth, Frank W.; Grindeland, Richard E.

    1995-01-01

    The objective of this study was to determine the ability of a single bout of resistance exercise alone or in combination with recombinant human growth hormone (rhGH) to stimulate myofibrillar protein synthesis (Ks) in hindlimb suspended (HLS) adult female rats. Plantar flexor muscles were stimulated with resistance exercise, consisting of 10 repetitions of ladder climbing on a 1 m grid (85 deg.), carrying an additional 50% of their body weight attached to their tails. Saline or rhGH (1 mg/kg) was administered 30' prior to exercise, and Ks was determined with a constant infusion of H-3-Leucine at 15', 60', 180', and 360' following exercise. Three days of HLS depressed Ks is approx. equal to 65% and 30-40% in the soleus and gastrocnemius muscles, respectively (p is less than or equal to 0.05). Exercise increased soleus Ks in saline-treated rats 149% 60' following exercise (p less than or equal to 0.05), decaying to that of non-exercised animals during the next 5 hours. Relative to suspended, non-exercised rats rhGH + exercise increased soleus Ks 84%, 108%, and 72% at 15', 60' and 360' following exercise (p is less than or equal to 0.05). Gastrocnemius Ks was not significantly increased by exercise or the combination of rhGH and exercise up to 360' post-exercise. Results from this study indicate that resistance exercise stimulated Ks 60' post-exercise in the soleus of HLS rats, with no apparent effect of rhGH to enhance or prolong exercise-induced stimulation. Results suggests that exercise frequency may be important to maintenance of the slow-twitch soleus during non-weightbearing, but that the ability of resistance exercise to maintain myofibrillar protein content in the gastrocnemius of hindlimb suspended rats cannot be explained by acute stimulation of synthesis.

  11. Reliability of a Novel High Intensity One Leg Dynamic Exercise Protocol to Measure Muscle Endurance

    PubMed Central

    Lepers, Romuald; Marcora, Samuele M.

    2016-01-01

    We recently developed a high intensity one leg dynamic exercise (OLDE) protocol to measure muscle endurance and investigate the central and peripheral mechanisms of muscle fatigue. The aims of the present study were to establish the reliability of this novel protocol and describe the isokinetic muscle fatigue induced by high intensity OLDE and its recovery. Eight subjects performed the OLDE protocol (time to exhaustion test of the right leg at 85% of peak power output) three times over a week period. Isokinetic maximal voluntary contraction torque at 60 (MVC60), 100 (MVC100) and 140 (MVC140) deg/s was measured pre-exercise, shortly after exhaustion (13 ± 4 s), 20 s (P20) and 40 s (P40) post-exercise. Electromyographic (EMG) signal was analyzed via the root mean square (RMS) for all three superficial knee extensors. Mean time to exhaustion was 5.96 ± 1.40 min, coefficient of variation was 8.42 ± 6.24%, typical error of measurement was 0.30 min and intraclass correlation was 0.795. MVC torque decreased shortly after exhaustion for all angular velocities (all P < 0.001). MVC60 and MVC100 recovered between P20 (P < 0.05) and exhaustion and then plateaued. MVC140 recovered only at P40 (P < 0.05). High intensity OLDE did not alter maximal EMG RMS of the three superficial knee extensors during MVC. The results of this study demonstrate that this novel high intensity OLDE protocol could be reliably used to measure muscle endurance, and that muscle fatigue induced by high intensity OLDE should be examined within ~ 30 s following exhaustion. PMID:27706196

  12. The Dynamics of Voluntary Force Production in Afferented Muscle Influence Involuntary Tremor

    PubMed Central

    Laine, Christopher M.; Nagamori, Akira; Valero-Cuevas, Francisco J.

    2016-01-01

    Voluntary control of force is always marked by some degree of error and unsteadiness. Both neural and mechanical factors contribute to these fluctuations, but how they interact to produce them is poorly understood. In this study, we identify and characterize a previously undescribed neuromechanical interaction where the dynamics of voluntary force production suffice to generate involuntary tremor. Specifically, participants were asked to produce isometric force with the index finger and use visual feedback to track a sinusoidal target spanning 5–9% of each individual's maximal voluntary force level. Force fluctuations and EMG activity over the flexor digitorum superficialis (FDS) muscle were recorded and their frequency content was analyzed as a function of target phase. Force variability in either the 1–5 or 6–15 Hz frequency ranges tended to be largest at the peaks and valleys of the target sinusoid. In those same periods, FDS EMG activity was synchronized with force fluctuations. We then constructed a physiologically-realistic computer simulation in which a muscle-tendon complex was set inside of a feedback-driven control loop. Surprisingly, the model sufficed to produce phase-dependent modulation of tremor similar to that observed in humans. Further, the gain of afferent feedback from muscle spindles was critical for appropriately amplifying and shaping this tremor. We suggest that the experimentally-induced tremor may represent the response of a viscoelastic muscle-tendon system to dynamic drive, and therefore does not fall into known categories of tremor generation, such as tremorogenic descending drive, stretch-reflex loop oscillations, motor unit behavior, or mechanical resonance. Our findings motivate future efforts to understand tremor from a perspective that considers neuromechanical coupling within the context of closed-loop control. The strategy of combining experimental recordings with physiologically-sound simulations will enable thorough

  13. Femoral strain during walking predicted with muscle forces from static and dynamic optimization.

    PubMed

    Edwards, W Brent; Miller, Ross H; Derrick, Timothy R

    2016-05-01

    Mechanical strain plays an important role in skeletal health, and the ability to accurately and noninvasively quantify bone strain in vivo may be used to develop preventive measures that improve bone quality and decrease fracture risk. A non-invasive estimation of bone strain requires combined musculoskeletal - finite element modeling, for which the applied muscle forces are usually obtained from static optimization (SO) methods. In this study, we compared finite element predicted femoral strains in walking using muscle forces obtained from SO to those obtained from forward dynamics (FD) simulation. The general trends in strain distributions were similar between FD and SO derived conditions and both agreed well with previously reported in vivo strain gage measurements. On the other hand, differences in peak maximum (εmax) and minimum (εmin) principal strain magnitudes were as high as 32% between FD (εmax/εmin=945/-1271με) and SO (εmax/εmin=752/-859με). These large differences in strain magnitudes were observed during the first half of stance, where SO predicted lower gluteal muscle forces and virtually no co-contraction of the hip adductors compared to FD. The importance of these results will likely depend on the purpose/application of the modeling procedure. If the goal is to obtain a generalized strain distribution for adaptive bone remodeling algorithms, then traditional SO is likely sufficient. In cases were strain magnitudes are critical, as is the case with fracture risk assessment, bone strain estimation may benefit by including muscle activation and contractile dynamics in SO, or by using FD when practical.

  14. The Dynamics of Voluntary Force Production in Afferented Muscle Influence Involuntary Tremor.

    PubMed

    Laine, Christopher M; Nagamori, Akira; Valero-Cuevas, Francisco J

    2016-01-01

    Voluntary control of force is always marked by some degree of error and unsteadiness. Both neural and mechanical factors contribute to these fluctuations, but how they interact to produce them is poorly understood. In this study, we identify and characterize a previously undescribed neuromechanical interaction where the dynamics of voluntary force production suffice to generate involuntary tremor. Specifically, participants were asked to produce isometric force with the index finger and use visual feedback to track a sinusoidal target spanning 5-9% of each individual's maximal voluntary force level. Force fluctuations and EMG activity over the flexor digitorum superficialis (FDS) muscle were recorded and their frequency content was analyzed as a function of target phase. Force variability in either the 1-5 or 6-15 Hz frequency ranges tended to be largest at the peaks and valleys of the target sinusoid. In those same periods, FDS EMG activity was synchronized with force fluctuations. We then constructed a physiologically-realistic computer simulation in which a muscle-tendon complex was set inside of a feedback-driven control loop. Surprisingly, the model sufficed to produce phase-dependent modulation of tremor similar to that observed in humans. Further, the gain of afferent feedback from muscle spindles was critical for appropriately amplifying and shaping this tremor. We suggest that the experimentally-induced tremor may represent the response of a viscoelastic muscle-tendon system to dynamic drive, and therefore does not fall into known categories of tremor generation, such as tremorogenic descending drive, stretch-reflex loop oscillations, motor unit behavior, or mechanical resonance. Our findings motivate future efforts to understand tremor from a perspective that considers neuromechanical coupling within the context of closed-loop control. The strategy of combining experimental recordings with physiologically-sound simulations will enable thorough exploration

  15. The Dynamics of Voluntary Force Production in Afferented Muscle Influence Involuntary Tremor

    PubMed Central

    Laine, Christopher M.; Nagamori, Akira; Valero-Cuevas, Francisco J.

    2016-01-01

    Voluntary control of force is always marked by some degree of error and unsteadiness. Both neural and mechanical factors contribute to these fluctuations, but how they interact to produce them is poorly understood. In this study, we identify and characterize a previously undescribed neuromechanical interaction where the dynamics of voluntary force production suffice to generate involuntary tremor. Specifically, participants were asked to produce isometric force with the index finger and use visual feedback to track a sinusoidal target spanning 5–9% of each individual's maximal voluntary force level. Force fluctuations and EMG activity over the flexor digitorum superficialis (FDS) muscle were recorded and their frequency content was analyzed as a function of target phase. Force variability in either the 1–5 or 6–15 Hz frequency ranges tended to be largest at the peaks and valleys of the target sinusoid. In those same periods, FDS EMG activity was synchronized with force fluctuations. We then constructed a physiologically-realistic computer simulation in which a muscle-tendon complex was set inside of a feedback-driven control loop. Surprisingly, the model sufficed to produce phase-dependent modulation of tremor similar to that observed in humans. Further, the gain of afferent feedback from muscle spindles was critical for appropriately amplifying and shaping this tremor. We suggest that the experimentally-induced tremor may represent the response of a viscoelastic muscle-tendon system to dynamic drive, and therefore does not fall into known categories of tremor generation, such as tremorogenic descending drive, stretch-reflex loop oscillations, motor unit behavior, or mechanical resonance. Our findings motivate future efforts to understand tremor from a perspective that considers neuromechanical coupling within the context of closed-loop control. The strategy of combining experimental recordings with physiologically-sound simulations will enable thorough

  16. Reproducible voluntary muscle performance during constant work rate dynamic leg exercise.

    PubMed

    Fulco, C S; Rock, P B; Muza, S R; Lammi, E; Cymerman, A; Lewis, S F

    2000-02-01

    During constant intensity treadmill or cycle exercise, progressive muscle fatigue is not readily quantified and endurance time is poorly reproducible. However, integration of dynamic knee extension (DKE) exercise with serial measurement of maximal voluntary contraction (MVC) force of knee extensor muscles permits close tracking of leg fatigue. We studied reproducibility of four performance indices: MVC force of rested muscle (MVC(rest)) rate of MVC force fall, time to exhaustion, and percentage of MVC(rest) (%MVC(rest)) at exhaustion in 11 healthy women (22+/-1 yrs) during identical constant work rate 1-leg DKE (1 Hz) on 2 separate days at sea level (30 m). Means+/-SD for the two test days, and the correlations (r), standard estimate errors and coefficients of variation (CV%) between days were, respectively: a) MVC(rest)(N), 524+/-99 vs 517+/-111, 0.91, 43.0, 4.9%; b) MVC force fall (N x min(-1)), -10.77+/-9.3 vs -11.79+/-12.1, 0.94, 3.6, 26.5 %; c) Time to exhaustion (min), 22.6+/-12 vs 23.9+/-14, 0.98, 2.7, 7.5 %; and d) %MVC(rest) at exhaustion, 65+/-13 vs 62+/-14, 0.85, 7.8, 5.6%. There were no statistically significant mean differences between the two test days for any of the performance measures. To demonstrate the potential benefits of evaluating multiple effects of an experimental intervention, nine of the women were again tested within 24hr of arriving at 4,300 m altitude using the identical force, velocity, power output, and energy requirement during constant work rate dynamic leg exercise. Low variability of each performance index enhanced the ability to describe the effects of acute altitude exposure on voluntary muscle function.

  17. Effects of Exercise on Soleus in Severe Burn and Muscle Disuse Atrophy

    PubMed Central

    Saeman, Melody R.; DeSpain, Kevin; Liu, Ming-Mei; Carlson, Brett A.; Song, Juquan; Baer, Lisa A.; Wade, Charles E.; Wolf, Steven E.

    2015-01-01

    Background Muscle loss is a sequela of severe burn and critical illness with bed rest contributing significantly to atrophy. We hypothesize that exercise will mitigate muscle loss after burn with bed rest. Materials and Methods Male rats were assigned to sham ambulatory (S/A), burn ambulatory (B/A), sham hindlimb unloading (S/H), or burn hindlimb unloading (B/H). Rats received a 40% scald burn or sham and were ambulatory or placed in hindlimb unloading, a model of bed rest. Half performed twice-daily resistance climbing. Hindlimb isometric forces were measured on day 14. Results Soleus mass and muscle function were not affected by burn alone. Mass was significantly lower in hindlimb unloading (79 vs.139 mg, p<0.001) and no exercise (103 vs.115 mg, p<0.01). Exercise significantly increased soleus mass in B/H (86 vs. 77mg, p<0.01). Hindlimb unloading significantly decreased muscle force in the twitch (31 vs. 12g, p<0.001), tetanic (55 vs. 148 g, p<0.001), and specific tetanic measurements (12 vs. 22 N/cm2, p<0.001). Effects of exercise on force depended on other factors. In B/H, exercise significantly increased twitch (14 vs. 8 g, p<0.05) and specific tetanic force (14 vs. 7 N/cm2, p<0.01). Fatigue index was lower in ambulatory (55%) and exercise (52%) versus hindlimb (69%, p=0.03) and no exercise (73%, p=0.002). Conclusions Hindlimb unloading is a significant factor in muscle atrophy. Exercise increased the soleus muscle mass, twitch, and specific force in this model. However, the fatigue index decreased with exercise in all groups. This suggests exercise contributes to functional muscle change in this model of disuse and critical illness. PMID:26104324

  18. The phylogeny of the red panda (Ailurus fulgens): evidence from the hindlimb.

    PubMed

    Fisher, Rebecca E; Adrian, Brent; Elrod, Clay; Hicks, Michelle

    2008-11-01

    The red panda (Ailurus fulgens) is an endangered carnivore living in the temperate forests of the Himalayas and southern China. The phylogeny of the red panda has been the subject of much debate. Morphological and molecular studies have supported a wide range of possible relationships, including close ties to procyonids, ursids, mustelids, and mephitids. This study provides additional morphological data, including muscle maps, for Ailurus. The hindlimbs of four cadavers from the National Zoological Park were dissected. Red pandas retain a number of muscles lost in other carnivore groups, including muscles and tendons related to their robust and weight-bearing hallux. Three features, including a single-bellied m. sartorius, a proximal insertion for m. abductor digiti V, and an absent m. articularis coxae, are found in all terrestrial arctoids, including Ailurus. In addition, red pandas are similar to ursids and canids in lacking a caudal belly of m. semitendinosus, while they resemble procyonids and mustelids in the degree of fusion observed between mm. gluteus medius and piriformis. Furthermore, Ailurus and procyonids are characterized by numerous subdivisions within the adductor compartment, while red pandas and raccoons share a variable m. semimembranosus, composed of one, two, or three bellies. Lastly, a deep plantar muscle inserting onto the metatarsophalangeal joint of the hallux is described for Ailurus. This muscle has not been previously described and is given the name m. flexor hallucis profundus. Additional dissections of the forelimb and axial musculature of red pandas may shed further light on the phylogeny of this species. In addition, the muscle maps presented here offer a valuable resource for interpreting the functional anatomy of fossil ailurids.

  19. The phylogeny of the red panda (Ailurus fulgens): evidence from the hindlimb

    PubMed Central

    Fisher, Rebecca E; Adrian, Brent; Elrod, Clay; Hicks, Michelle

    2008-01-01

    The red panda (Ailurus fulgens) is an endangered carnivore living in the temperate forests of the Himalayas and southern China. The phylogeny of the red panda has been the subject of much debate. Morphological and molecular studies have supported a wide range of possible relationships, including close ties to procyonids, ursids, mustelids, and mephitids. This study provides additional morphological data, including muscle maps, for Ailurus. The hindlimbs of four cadavers from the National Zoological Park were dissected. Red pandas retain a number of muscles lost in other carnivore groups, including muscles and tendons related to their robust and weight-bearing hallux. Three features, including a single-bellied m. sartorius, a proximal insertion for m. abductor digiti V, and an absent m. articularis coxae, are found in all terrestrial arctoids, including Ailurus. In addition, red pandas are similar to ursids and canids in lacking a caudal belly of m. semitendinosus, while they resemble procyonids and mustelids in the degree of fusion observed between mm. gluteus medius and piriformis. Furthermore, Ailurus and procyonids are characterized by numerous subdivisions within the adductor compartment, while red pandas and raccoons share a variable m. semimembranosus, composed of one, two, or three bellies. Lastly, a deep plantar muscle inserting onto the metatarsophalangeal joint of the hallux is described for Ailurus. This muscle has not been previously described and is given the name m. flexor hallucis profundus. Additional dissections of the forelimb and axial musculature of red pandas may shed further light on the phylogeny of this species. In addition, the muscle maps presented here offer a valuable resource for interpreting the functional anatomy of fossil ailurids. PMID:19014366

  20. The phylogeny of the red panda (Ailurus fulgens): evidence from the hindlimb.

    PubMed

    Fisher, Rebecca E; Adrian, Brent; Elrod, Clay; Hicks, Michelle

    2008-11-01

    The red panda (Ailurus fulgens) is an endangered carnivore living in the temperate forests of the Himalayas and southern China. The phylogeny of the red panda has been the subject of much debate. Morphological and molecular studies have supported a wide range of possible relationships, including close ties to procyonids, ursids, mustelids, and mephitids. This study provides additional morphological data, including muscle maps, for Ailurus. The hindlimbs of four cadavers from the National Zoological Park were dissected. Red pandas retain a number of muscles lost in other carnivore groups, including muscles and tendons related to their robust and weight-bearing hallux. Three features, including a single-bellied m. sartorius, a proximal insertion for m. abductor digiti V, and an absent m. articularis coxae, are found in all terrestrial arctoids, including Ailurus. In addition, red pandas are similar to ursids and canids in lacking a caudal belly of m. semitendinosus, while they resemble procyonids and mustelids in the degree of fusion observed between mm. gluteus medius and piriformis. Furthermore, Ailurus and procyonids are characterized by numerous subdivisions within the adductor compartment, while red pandas and raccoons share a variable m. semimembranosus, composed of one, two, or three bellies. Lastly, a deep plantar muscle inserting onto the metatarsophalangeal joint of the hallux is described for Ailurus. This muscle has not been previously described and is given the name m. flexor hallucis profundus. Additional dissections of the forelimb and axial musculature of red pandas may shed further light on the phylogeny of this species. In addition, the muscle maps presented here offer a valuable resource for interpreting the functional anatomy of fossil ailurids. PMID:19014366

  1. Differences in structural dynamics of muscle and yeast actin accompany differences in functional interactions with myosin.

    PubMed

    Prochniewicz, E; Thomas, D D

    1999-11-01

    We have used spectroscopic probes ErIA and IAEDANS attached to Cys374 to compare the structural dynamics of yeast actin filaments with that of muscle actin, to understand the structural basis of the less productive interaction of yeast actin with myosin. Time-resolved phosphorescence anisotropy (TPA) of ErIA and steady-state fluorescence of IAEDANS were measured. TPA indicated more rapid rotational motion and more restricted angular amplitude in yeast actin. The fluorescence spectrum was less intense and more red-shifted in yeast actin, suggesting more exposure of the probe to solvent. These results indicate that the two actins differ substantially in the conformational dynamics of the C-terminal region. Binding of myosin S1 induced significantly different spectroscopic changes in TPA and fluorescence of muscle and yeast actin. As a result, the spectroscopic differences between the two actins were decreased by the addition of S1. These results suggest that yeast actin is less effective at activating myosin because of larger changes required in the structure of actin upon strong myosin binding. These results provide insight into the relationship between actomyosin dynamics and function, and they provide a useful framework for structure-function analysis of mutant yeast actin.

  2. Effect of training on the muscle strength and dynamic balance ability of adults with down syndrome.

    PubMed

    Tsimaras, Vassilios K; Fotiadou, Eleni G

    2004-05-01

    The purpose of this study was to evaluate the effect of training on the muscle strength and dynamic balance ability of adults with Down syndrome (DS). Twenty-five adults with DS were separated into 2 groups. Fifteen subjects (mean age, 24.5 years) constituted the experiment group, whereas 10 subjects (mean age, 24.7 years) were in the control group of the study. Parameters measured were peak torque, isokinetic muscle endurance, and dynamic balance ability. All subjects performed a leg strength test on a Cyber II isokinetic dynamometer. In addition, the subjects' dynamic balance ability was measured by means of a balance deck (Lafayette). The experimental group followed a 12-week training program. As the results indicated, the experimental group showed a statistically significant improvement in all measured values when compared with the control group. It is concluded that adults with DS can improve their physical and kinetic abilities with the application of a systematic and well-designed training program.

  3. Electromyographic responses of erector spinae and lower limb's muscles to dynamic postural perturbations in patients with adolescent idiopathic scoliosis.

    PubMed

    Farahpour, Nader; Ghasemi, Safoura; Allard, Paul; Saba, Mohammad Sadegh

    2014-10-01

    The aim of this study was to evaluate electromyographic (EMG) responses of erector spinae (ES) and lower limbs' muscles to dynamic forward postural perturbation (FPP) and backward postural perturbation (BPP) in patients with adolescent idiopathic scoliosis (AIS) and in a healthy control group. Ten right thoracic AIS patients (Cobb=21.6±4.4°) and 10 control adolescents were studied. Using bipolar surface electrodes, EMG activities of ES muscle at T10 (EST10) and L3 (ESL3) levels, biceps femoris (BF), gastrocnemius lateralis (G) and rectus femoris (RF) muscles in the right and the left sides during FPP and BPP were evaluated. Muscle responses were measured over a 1s time window after the onset of perturbation. In FPP test, the EMG responses of right EST10, ESL3 and BF muscles in the scoliosis group were respectively about 1.40 (p=0.035), 1.43 (p=0.07) and 1.45 (p=0.01) times greater than those in control group. Also, in BPP test, at right ESL3 muscle of the scoliosis group the EMG activity was 1.64 times higher than that in the control group (p=0.01). The scoliosis group during FPP displayed asymmetrical muscle responses in EST10 and BF muscles. This asymmetrical muscle activity in response to FPP is hypothesized to be a possible compensatory strategy rather than an inherent characteristic of scoliosis.

  4. Polymer-DNA Nanoparticle-Induced CXCR4 Overexpression Improves Stem Cell Engraftment and Tissue Regeneration in a Mouse Hindlimb Ischemia Model

    PubMed Central

    Deveza, Lorenzo; Choi, Jeffrey; Lee, Jerry; Huang, Ngan; Cooke, John; Yang, Fan

    2016-01-01

    Peripheral arterial disease affects nearly 202 million individuals worldwide, sometimes leading to non-healing ulcers or limb amputations in severe cases. Genetically modified stem cells offer potential advantages for therapeutically inducing angiogenesis via augmented paracrine release mechanisms and tuned dynamic responses to environmental stimuli at disease sites. Here, we report the application of nanoparticle-induced CXCR4-overexpressing stem cells in a mouse hindlimb ischemia model. We found that CXCR4 overexpression improved stem cell survival, modulated inflammation in situ, and accelerated blood reperfusion. These effects, unexpectedly, led to complete limb salvage and skeletal muscle repair, markedly outperforming the efficacy of the conventional angiogenic factor control, VEGF. Importantly, assessment of CXCR4-overexpressing stem cells in vitro revealed that CXCR4 overexpression induced changes in paracrine signaling of stem cells, promoting a therapeutically desirable pro-angiogenic and anti-inflammatory phenotype. These results suggest that nanoparticle-induced CXCR4 overexpression may promote favorable phenotypic changes and therapeutic efficacy of stem cells in response to the ischemic environment. PMID:27279910

  5. Exercise effects on the size and metabolic properties of soleus fibers in hindlimb-suspended rats

    NASA Technical Reports Server (NTRS)

    Graham, Scot C.; Roy, Roland R.; West, Steve P.; Thomason, Don; Baldwin, Kenneth M.

    1989-01-01

    The effects of four-week-long hind-limb suspension (HS) of rats on the size the soleus muscle fibers and the activity of succinate dehydrogenase (SDH) in dark and light ATPase fibers were investigated together with the efficacy of an endurance exercise (EX) program (daily treadmill exercise for 1.5 h/day at 20 m/min and a 30-percent grade) in ameliorating HS-induced changes. It was found that, in comparison to age-matched controls, the soleus wet weight decreased by 69 and 30 percent in HS and HS-EX rats, respectively, and the percent of dark ATPase fibers increased from 10 percent in controls to 19 and 17 percent, respectively. The values of the integrated fiber activity (activity/min times muscle area) showed a net loss of SDH in both the light and dark ATPase fibers of HS rats, but only in the light ATPase fibers of the HS-EX rats, indicating that exercise ameliorated but did not prevent the muscle fiber atrophy induced by HS.

  6. Computational model of cellular metabolic dynamics: effect of insulin on glucose disposal in human skeletal muscle.

    PubMed

    Li, Yanjun; Solomon, Thomas P J; Haus, Jacob M; Saidel, Gerald M; Cabrera, Marco E; Kirwan, John P

    2010-06-01

    Identifying the mechanisms by which insulin regulates glucose metabolism in skeletal muscle is critical to understanding the etiology of insulin resistance and type 2 diabetes. Our knowledge of these mechanisms is limited by the difficulty of obtaining in vivo intracellular data. To quantitatively distinguish significant transport and metabolic mechanisms from limited experimental data, we developed a physiologically based, multiscale mathematical model of cellular metabolic dynamics in skeletal muscle. The model describes mass transport and metabolic processes including distinctive processes of the cytosol and mitochondria. The model simulated skeletal muscle metabolic responses to insulin corresponding to human hyperinsulinemic-euglycemic clamp studies. Insulin-mediated rate of glucose disposal was the primary model input. For model validation, simulations were compared with experimental data: intracellular metabolite concentrations and patterns of glucose disposal. Model variations were simulated to investigate three alternative mechanisms to explain insulin enhancements: Model 1 (M.1), simple mass action; M.2, insulin-mediated activation of key metabolic enzymes (i.e., hexokinase, glycogen synthase, pyruvate dehydrogenase); or M.3, parallel activation by a phenomenological insulin-mediated intracellular signal that modifies reaction rate coefficients. These simulations indicated that models M.1 and M.2 were not sufficient to explain the experimentally measured metabolic responses. However, by application of mechanism M.3, the model predicts metabolite concentration changes and glucose partitioning patterns consistent with experimental data. The reaction rate fluxes quantified by this detailed model of insulin/glucose metabolism provide information that can be used to evaluate the development of type 2 diabetes.

  7. Characterization of beta-connectin (titin 2) from striated muscle by dynamic light scattering.

    PubMed Central

    Higuchi, H; Nakauchi, Y; Maruyama, K; Fujime, S

    1993-01-01

    Connectin (titin) is a large filamentous protein (single peptide) with a molecular mass of approximately 3 MDa, contour length approximately 900 nm, and diameter approximately 4 nm, and resides in striated muscle. Connectin links the thick filaments to the Z-lines in a sarcomere and produces a passive elastic force when muscle fiber is stretched. The aim of this study is to elucidate some aspects of physical properties of isolated beta-connectin (titin 2), a proteolytic fragment of connectin, by means of dynamic light-scattering (DLS) spectroscopy. The analysis of DLS spectra for beta-connectin gave the translational diffusion coefficient of 3.60 x 10(-8) cm2/s at 10 degrees C (or the hydrodynamic radius of 44.1 nm), molecular mass little smaller than 3.0 MDa (for a literature value of sedimentation coefficient), the root-mean-square end-to-end distance of 163 nm (or the radius of gyration of 66.6 nm), and the Kuhn segment number of 30 and segment length of 30 nm (or the persistence length of 15 nm). These results permitted to estimate the flexural rigidity of 6.0 x 10(-20) dyn x cm2 for filament bending, and the elastic constant of 7 dyn/cm for extension of one persistence length. Based on a simple model, implications of the present results in muscle physiology are discussed. Images FIGURE 1 PMID:8298020

  8. The Dynamic Behaviour and Shock Recovery of a Porcine Skeletal Muscle Tissue

    NASA Astrophysics Data System (ADS)

    Wilgeroth, James; Hazell, Paul; Appleby-Thomas, Gareth

    2011-06-01

    Modern-day ballistic armours provide a high degree of protection to the individual. However, the effects of non-penetrating projectiles, blast, and high-energy blunt impact events may still cause severe tissue trauma/remote injury. The energies corresponding to such events allow for the formation and transmission of shock waves within body tissues. Consequently, the nature of trauma inflicted upon such soft tissues is likely to be intimately linked to their interaction with the shock waves that propagate through them. Notably, relatively little is known about the effect of shock upon the structure of biological materials, such as skeletal muscle tissue. In this study plate-impact experiments have been used to interrogate the dynamic response of a porcine skeletal muscle tissue under one-dimensional shock loading conditions. Additionally, development of a soft-capture system that has allowed recovery of shocked skeletal muscle tissue specimens is discussed and comparison made between experimental diagnostics and hydrocode simulations of the experiment.

  9. Development of Sensory Receptors in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    DeSantis, Mark

    2000-01-01

    The two major goals for this project is to (1) examine the hindlimb walking pattern of offspring from the Flight dams as compared with offspring of the ground control groups from initiation of walking up to two months thereafter; and (2) examine skeletal muscle.

  10. Effects of inspiratory muscle training on dynamic hyperinflation in patients with COPD.

    PubMed

    Petrovic, Milos; Reiter, Michael; Zipko, Harald; Pohl, Wolfgang; Wanke, Theodor

    2012-01-01

    Dynamic hyperinflation has important clinical consequences in patients with chronic obstructive pulmonary disease (COPD). Given that most of these patients have respiratory and peripheral muscle weakness, dyspnea and functional exercise capacity may improve as a result of inspiratory muscle training (IMT). The aim of the study was to analyze the effects of IMT on exercise capacity, dyspnea, and inspiratory fraction (IF) during exercise in patients with COPD. Daily inspiratory muscle strength and endurance training was performed for 8 weeks in 10 patients with COPD GOLD II and III. Ten patients with COPD II and III served as a control group. Maximal inspiratory pressure (Pimax) and endurance time during resistive breathing maneuvers (tlim) served as parameter for inspiratory muscle capacity. Before and after training, the patients performed an incremental symptom limited exercise test to maximum and a constant load test on a cycle ergometer at 75% of the peak work rate obtained in the pretraining incremental test. ET was defined as the duration of loaded pedaling. Following IMT, there was a statistically significant increase in inspiratory muscle performance of the Pimax from 7.75 ± 0.47 to 9.15 ± 0.73 kPa (P < 0.01) and of tlim from 348 ± 54 to 467 ± 58 seconds (P < 0.01). A significant increase in IF, indicating decreased dynamic hyperinflation, was observed during both exercise tests. Further, the ratio of breathing frequency to minute ventilation (bf/V'(E)) decreased significantly, indicating an improved breathing pattern. A significant decrease in perception of dyspnea was also measured. Peak work rate during the incremental cycle ergometer test remained constant, while ET during the constant load test increased significantly from 597.1 ± 80.8 seconds at baseline to 733.6 ± 74.3 seconds (P < 0.01). No significant changes during either exercise tests were measured in the control group. The present study found that in patients with COPD, IMT results in

  11. Ultrasound-induced microbubble destruction promotes targeted delivery of adipose-derived stem cells to improve hind-limb ischemia of diabetic mice.

    PubMed

    Song, Ye; Xie, Xiaoyun; Gao, Yuan; Gu, Guojun; Wang, Peijun

    2016-01-01

    This study aimed to investigate whether ultrasound-induced microbubble destruction was able to promote targeted delivery of adipose-derived stem cells (ASCs) to improve hind-limb ischemia of diabetic mice. Ischemia was induced in the lower limb of db/db mice which were then randomly divided into 5 groups: PBS group, Sham group, ultrasound + microbubble group (US+MB), US+MB+ASCs group and ASCs group. Contrast-enhanced ultrasound perfusion imaging showed the ratio of blood flow in ischemic hind-limb to that in contralateral limb increased over time in five groups. A significant enhancement in US+MB+ASCs group was observed compared with US+MB group (P<0.01). Immunofluorescence microscopy of hind-limb muscle showed the microvessel density (microvessels/skeletal muscle fibers) and arteriolar density in US+MB+ASCs group were higher than in US+MB group, and significantly higher than in other control groups (P<0.01). Masson staining indicated the degree of muscle fibrosis in US+MB+ASCs group was lower than in US+MB. 3 and 7 days after therapy, ELISA and RT-PCR showed the expression of VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than in US+MB group, and dramatically increased as compared to other groups (P<0.01). 3 and 7 days after therapy, Western blot assay showed the protein expression of P-P13K, P-AKT, VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than US+MB group (P<0.01). The bioeffects of ultrasound-induced microbubble cavitation is able to up-regulate the expression of pro-inflammatory cytokines, which may improve the targeted delivery, adhesion and paracrine of ASCs, attenuating the hind-limb ischemia in diabetic mice. PMID:27398142

  12. Ultrasound-induced microbubble destruction promotes targeted delivery of adipose-derived stem cells to improve hind-limb ischemia of diabetic mice

    PubMed Central

    Song, Ye; Xie, Xiaoyun; Gao, Yuan; Gu, Guojun; Wang, Peijun

    2016-01-01

    This study aimed to investigate whether ultrasound-induced microbubble destruction was able to promote targeted delivery of adipose-derived stem cells (ASCs) to improve hind-limb ischemia of diabetic mice. Ischemia was induced in the lower limb of db/db mice which were then randomly divided into 5 groups: PBS group, Sham group, ultrasound + microbubble group (US+MB), US+MB+ASCs group and ASCs group. Contrast-enhanced ultrasound perfusion imaging showed the ratio of blood flow in ischemic hind-limb to that in contralateral limb increased over time in five groups. A significant enhancement in US+MB+ASCs group was observed compared with US+MB group (P<0.01). Immunofluorescence microscopy of hind-limb muscle showed the microvessel density (microvessels/skeletal muscle fibers) and arteriolar density in US+MB+ASCs group were higher than in US+MB group, and significantly higher than in other control groups (P<0.01). Masson staining indicated the degree of muscle fibrosis in US+MB+ASCs group was lower than in US+MB. 3 and 7 days after therapy, ELISA and RT-PCR showed the expression of VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than in US+MB group, and dramatically increased as compared to other groups (P<0.01). 3 and 7 days after therapy, Western blot assay showed the protein expression of P-P13K, P-AKT, VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than US+MB group (P<0.01). The bioeffects of ultrasound-induced microbubble cavitation is able to up-regulate the expression of pro-inflammatory cytokines, which may improve the targeted delivery, adhesion and paracrine of ASCs, attenuating the hind-limb ischemia in diabetic mice. PMID:27398142

  13. Evaluation of Driver-vehicle Matching using Neck Muscle Activity and Vehicle Dynamics

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yoshiki; Umetsu, Daisuke; Ozaki, Shigeru

    Objective measurement of a car driver's feeling has been a subject of automobile researches. In the present study, we aimed at quantifying the matching between the physiological response of a driver and the vehicle motion. Assuming that the performance of a head stabilization mechanism, the vestibulo-collic reflex, affects driving feeling, we recorded the activity of neck muscles that help maintain the head position. Electromyograms (EMGs) were recorded from the sternocleidomastoid muscles (SCM) using active electrodes and a compact amplifier. Vehicle acceleration and gas pedal movement were recorded with small accelerometers. Subjects were required to perform straight-line acceleration. Four road cars with different characteristics were used. EMG signals were filtered, full-wave rectified and averaged across trials. Main results are summarized as follows. First, the EMG response of a driver's neck muscle depended not only on vehicle acceleration but on its time derivative, jerk. A quantitative analysis showed that, for the data obtained with the four cars, the EMG profile can be reproduced by a linear sum of acceleration and jerk. The correlation coefficient, an index of goodness of matching, ranged from ~0.8 to ~0.95. Second, our analysis indicated that the relationship between the muscle response and the vehicle motion can be characterized by two parameters: the optimal weight for the jerk term and the optimal time lag. The current study proposes a method for characterizing a physiological response of a driver to dynamic vehicle motion. It remains to be investigated whether these parameters are related to the driving feeling.

  14. Modeling Energy Dynamics in Mice with Skeletal Muscle Hypertrophy Fed High Calorie Diets

    PubMed Central

    Bond, Nichole D.; Guo, Juen; Hall, Kevin D.; McPherron, Alexandra C.

    2016-01-01

    Retrospective and prospective studies show that lean mass or strength is positively associated with metabolic health. Mice deficient in myostatin, a growth factor that negatively regulates skeletal muscle mass, have increased muscle and body weights and are resistant to diet-induced obesity. Their leanness is often attributed to higher energy expenditure in the face of normal food intake. However, even obese animals have an increase in energy expenditure compared to normal weight animals suggesting this is an incomplete explanation. We have previously developed a computational model to estimate energy output, fat oxidation and respiratory quotient from food intake and body composition measurements to more accurately account for changes in body composition in rodents over time. Here we use this approach to understand the dynamic changes in energy output, intake, fat oxidation and respiratory quotient in muscular mice carrying a dominant negative activin receptor IIB expressed specifically in muscle. We found that muscular mice had higher food intake and higher energy output when fed either chow or a high-fat diet for 15 weeks compared to WT mice. Transgenic mice also matched their rate of fat oxidation to the rate of fat consumed better than WT mice. Surprisingly, when given a choice between high-fat diet and Ensure® drink, transgenic mice consumed relatively more calories from Ensure® than from the high-fat diet despite similar caloric intake to WT mice. When switching back and forth between diets, transgenic mice adjusted their intake more rapidly than WT to restore normal caloric intake. Our results show that mice with myostatin inhibition in muscle are better at adjusting energy intake and output on diets of different macronutrient composition than WT mice to maintain energy balance and resist weight gain. PMID:27076790

  15. Thermal effects on the performance, motor control and muscle dynamics of ballistic feeding in the salamander Eurycea guttolineata.

    PubMed

    Anderson, Christopher V; Larghi, Nicholas P; Deban, Stephen M

    2014-09-01

    Temperature strongly affects muscle contractile rate properties and thus may influence whole-organism performance. Movements powered by elastic recoil, however, are known to be more thermally robust than muscle-powered movements. We examined the whole-organism performance, motor control and muscle contractile physiology underlying feeding in the salamander Eurycea guttolineata. We compared elastically powered tongue projection with the associated muscle-powered retraction to determine the thermal robustness of each of these functional levels. We found that tongue-projection distance in E. guttolineata was unaffected by temperature across the entire 4-26°C range, tongue-projection dynamics were significantly affected by temperature across only the 4-11°C interval, and tongue retraction was affected to a higher degree across the entire temperature range. The significant effect of temperature on projection dynamics across the 4-11°C interval corresponds to a significant decline in projector muscle burst intensity and peak contractile force of the projector muscle across the same interval. Across the remaining temperature range, however, projection dynamics were unaffected by temperature, with muscle contractile physiology showing typical thermal effects and motor patterns showing increased activity durations and latencies. These results reveal that elastically powered tongue-projection performance in E. guttolineata is maintained to a higher degree than muscle-powered tongue retraction performance across a wide temperature range. These results further indicate that thermal robustness of the elastically powered movement is dependent on motor control and muscle physiology that results in comparable energy being stored in elastic tissues across a range of temperatures.

  16. Alterations in skeletal muscle related to impaired physical mobility: an empirical model

    NASA Technical Reports Server (NTRS)

    Kasper, C. E.; McNulty, A. L.; Otto, A. J.; Thomas, D. P.

    1993-01-01

    The objective of this investigation was to study impaired physical mobility and the resulting skeletal muscle atrophy. An animal model was used to study morphological adaptations of the soleus and plantaris muscles to decreased loading induced by hindlimb suspension of an adult rat for 7, 14, and 28 consecutive days. Alterations in weight, skeletal muscle growth, and changes in fiber type composition were studied in synergistic plantar flexors of the rat hindlimb. Body weight and the soleus muscle mass to body mass ratio demonstrated significant progressive atrophy over th 28-day experimental period with the most significant changes occurring in the first 7 days of hindlimb suspension. Hindlimb suspension produced atrophy of Type I and Type IIa muscle fibers as demonstrated by significant decreases in fiber cross-sectional area (micron 2). These latter changes account for the loss of contractile force production reported in the rat following hindlimb unloading. When compared to traditional models of hindlimb suspension and immobilization, the ISC model produces a less severe atrophy while maintaining animal mobility and health. We conclude that it is the preferred animal model to address nursing questions of impaired physical mobility.

  17. Temporal Co-Variation between Eye Lens Accommodation and Trapezius Muscle Activity during a Dynamic Near-Far Visual Task

    PubMed Central

    Zetterberg, Camilla; Richter, Hans O.; Forsman, Mikael

    2015-01-01

    Near work is associated with increased activity in the neck and shoulder muscles, but the underlying mechanism is still unknown. This study was designed to determine whether a dynamic change in focus, alternating between a nearby and a more distant visual target, produces a direct parallel change in trapezius muscle activity. Fourteen healthy controls and 12 patients with a history of visual and neck/shoulder symptoms performed a Near-Far visual task under three different viewing conditions; one neutral condition with no trial lenses, one condition with negative trial lenses to create increased accommodation, and one condition with positive trial lenses to create decreased accommodation. Eye lens accommodation and trapezius muscle activity were continuously recorded. The trapezius muscle activity was significantly higher during Near than during Far focusing periods for both groups within the neutral viewing condition, and there was a significant co-variation in time between accommodation and trapezius muscle activity within the neutral and positive viewing conditions for the control group. In conclusion, these results reveal a connection between Near focusing and increased muscle activity during dynamic changes in focus between a nearby and a far target. A direct link, from the accommodation/vergence system to the trapezius muscles cannot be ruled out, but the connection may also be explained by an increased need for eye-neck (head) stabilization when focusing on a nearby target as compared to a more distant target. PMID:25961299

  18. Dynamics of a pneumatic artificial muscle actuation system driving a trailing edge flap

    NASA Astrophysics Data System (ADS)

    Woods, Benjamin K. S.; Kothera, Curt S.; Wang, Gang; Wereley, Norman M.

    2014-09-01

    This study presents a time domain dynamic model of an antagonistic pneumatic artificial muscle (PAM) driven trailing edge flap (TEF) system for next generation active helicopter rotors. Active rotor concepts are currently being widely researched in the rotorcraft community as a means to provide a significant leap forward in performance through primary aircraft control, vibration mitigation and noise reduction. Recent work has shown PAMs to be a promising candidate for active rotor actuation due to their combination of high force, large stroke, light weight, and suitable bandwidth. When arranged into biologically inspired agonist/antagonist muscle pairs they can produce bidirectional torques for effectively driving a TEF. However, there are no analytical dynamic models in the literature that can accurately capture the behavior of such systems across the broad range of frequencies required for this demanding application. This work combines mechanical, pneumatic, and aerodynamic component models into a global flap system model developed for the Bell 407 rotor system. This model can accurately predict pressure, force, and flap angle response to pneumatic control valve inputs over a range of operating frequencies from 7 to 35 Hz (1/rev to 5/rev for the Bell 407) and operating pressures from 30 to 90 psi.

  19. Dynamic coupling of regulated binding sites and cycling myosin heads in striated muscle.

    PubMed

    Campbell, Kenneth S

    2014-03-01

    In an activated muscle, binding sites on the thin filament and myosin heads switch frequently between different states. Because the status of the binding sites influences the status of the heads, and vice versa, the binding sites and myosin heads are dynamically coupled. The functional consequences of this coupling were investigated using MyoSim, a new computer model of muscle. MyoSim extends existing models based on Huxley-type distribution techniques by incorporating Ca(2+) activation and cooperative effects. It can also simulate arbitrary cross-bridge schemes set by the researcher. Initial calculations investigated the effects of altering the relative speeds of binding-site and cross-bridge kinetics, and of manipulating cooperative processes. Subsequent tests fitted simulated force records to experimental data recorded using permeabilized myocardial preparations. These calculations suggest that the rate of force development at maximum activation is limited by myosin cycling kinetics, whereas the rate at lower levels of activation is limited by how quickly binding sites become available. Additional tests investigated the behavior of transiently activated cells by driving simulations with experimentally recorded Ca(2+) signals. The unloaded shortening profile of a twitching myocyte could be reproduced using a model with two myosin states, cooperative activation, and strain-dependent kinetics. Collectively, these results demonstrate that dynamic coupling of binding sites and myosin heads is important for contractile function.

  20. Bone, blood vessels, and muscle detection algorithm and creating database based on dynamic and non-dynamic multi-slice CT image of head and neck

    NASA Astrophysics Data System (ADS)

    Shabbir Ahamed, Mohammed; Kubo, Mitsuru; Kawata, Yoshiki; Niki, Noboru; Iwasaki, Hirokazu

    2007-03-01

    Nowadays, dental CT images play more and more important roles in oral clinical applications. Our research is important particularly in the field of dentistry. We are using non-dynamic and dynamic CT image for our research. We are creating our database of bone, blood vessels and muscles of head and neck. This database contains easy case and difficult case of head and neck's bone, blood vessels and muscle. There are lots of difficult cases in our database. Teeth separation and condylar process separation is difficult case. External carotid artery has many branches and they are attached with vain so it is difficult to separate. All muscle threshold value is same and they are attaching with each other so muscle separation is very difficult. These databases also contain different age's patients. For this reason our database becomes an important tool for dental students and also important assets for diagnosis. After completion our database we can link it with other dental application.

  1. Expression of IGF-I and Protein Degradation Markers During Hindlimb Unloading and Growth Hormone Administration in Rats

    NASA Astrophysics Data System (ADS)

    Leinsoo, T. A.; Turtikova, O. V.; Shenkman, B. S.

    2013-02-01

    It is known that hindlimb unloading or spaceflight produce atrophy and a number of phenotypic alterations in skeletal muscles. Many of these processes are triggered by the axis growth hormone/insulin-like growth factor I. However growth hormone (GH) and insulin-like growth factor I (IGF-I) expression relationship in rodent models of gravitational unloading is weakly investigated. We supposed the IGF-I is involved in regulation of protein turnover. In this study we examined the IGF-I expression by RT-PCR assay in the rat soleus, tibialis anterior and liver after 3 day of hindlimb suspension with growth hormone administration. Simultaneously were studied expression levels of MuRF-1 and MAFbx/atrogin as a key markers of intracellular proteolysis. We demonstrated that GH administration did not prevent IGF-I expression decreasing under the conditions of simulated weightlessness. It was concluded there are separate mechanisms of action of GH and IGF-I on protein metabolism in skeletal muscles. Gravitational unloading activate proteolysis independently of growth hormone activity.

  2. Modeling the Peano fluidic muscle and the effects of its material properties on its static and dynamic behavior

    NASA Astrophysics Data System (ADS)

    Veale, Allan Joshua; Xie, Sheng Quan; Anderson, Iain Alexander

    2016-06-01

    The promise of wearable assistive robotics cannot be realized without the development of actuators that mimic the behavior and form of biological muscles. Planar fluidic muscles known as Peano muscles or pouch motors have the potential to provide the high force and compliance of McKibben pneumatic artificial muscles with the low threshold pressure of pleated pneumatic artificial muscles. Yet they do so in a soft and slim form that can be discreetly distributed over the human body. This work is an investigation into the empirical modeling of the Peano muscle, the effect of its material on its performance, and its capabilities and limitations. We discovered that the Peano muscle could provide responsive and discreet actuation of soft and rigid bodies requiring strains between 15% and 30%. Ideally, they are made of non-viscoelastic materials with high tensile and low bending stiffnesses. While Sarosi et al’s empirical model accurately captures its static behavior with an root mean square error of 10.2 N, their dynamic model overestimates oscillation frequency and damping. We propose that the Peano muscle be modeled by a parallel ideal contractile unit and viscoelastic element, both in series with another viscoelastic element.

  3. Complement activation promotes muscle inflammation during modified muscle use

    NASA Technical Reports Server (NTRS)

    Frenette, J.; Cai, B.; Tidball, J. G.

    2000-01-01

    Modified muscle use can result in muscle inflammation that is triggered by unidentified events. In the present investigation, we tested whether the activation of the complement system is a component of muscle inflammation that results from changes in muscle loading. Modified rat hindlimb muscle loading was achieved by removing weight-bearing from the hindlimbs for 10 days followed by reloading through normal ambulation. Experimental animals were injected with the recombinant, soluble complement receptor sCR1 to inhibit complement activation. Assays for complement C4 or factor B in sera showed that sCR1 produced large reductions in the capacity for activation of the complement system through both the classical and alternative pathways. Analysis of complement C4 concentration in serum in untreated animals showed that the classical pathway was activated during the first 2 hours of reloading. Analysis of factor B concentration in untreated animals showed activation of the alternative pathway at 6 hours of reloading. Administration of sCR1 significantly attenuated the invasion of neutrophils (-49%) and ED1(+) macrophages (-52%) that occurred in nontreated animals after 6 hours of reloading. The presence of sCR1 also reduced significantly the degree of edema by 22% as compared to untreated animals. Together, these data show that increased muscle loading activated the complement system which then briefly contributes to the early recruitment of inflammatory cells during modified muscle loading.

  4. Dynamics of circus movement re-entry across canine Purkinje fibre-muscle junctions.

    PubMed

    Gilmour, R F; Watanabe, M

    1994-05-01

    1. To determine the cellular electrophysiological mechanisms for unidirectional conduction block and re-entrant excitation, single cycles of circus movement re-entry were induced in canine Purkinje fibre-papillary muscle preparations containing two Purkinje fibre-muscle junctions (PMJs). The preparations were mounted in a partitioned tissue bath that permitted independent superfusion of each PMJ. The pre-existing dispersion of refractoriness between PMJs was accentuated by superfusing PMJ1 with normal Tyrode solution or Tyrode solution containing 6-8 mM KCl and superfusing PMJ2 with Tyrode solution containing 0.5 mM heptanol and 4-10 mM KCl. 2. Premature stimuli delivered to the Purkinje fibre induced unidirectional anterograde conduction block at PMJ2. Conduction proceeded from Purkinje cells to papillary muscle at PMJ1 and from papillary muscle retrogradely across the previously blocked PMJ2. 3. The difference in refractory periods between the two PMJs defined a range of premature coupling intervals within which re-entry was inducible. Conduction block at the PMJ occurred in papillary muscle at short coupling intervals and in the Purkinje fibre at longer intervals. 4. Once initiated, re-entry could be reset or annihilated by properly timed subthreshold current pulses delivered to cells at the PMJ. 5. To define better the mechanisms for conduction block and re-entry, an analytical model was developed using non-linear regression analysis to derive equations from the experimental results. Varying parameters within the constraints of the model reproduced the key features of the rate-dependent conduction block observed experimentally. Critical elements of the model included the induction of significant activation delays at short diastolic intervals and a reduction in the rate of action potential duration restitution after exposure to heptanol. 6. These results help to establish the conditions necessary for induction of one-dimensional circus movement re-entry and to

  5. Far red/near infrared light treatment promotes femoral artery collateralization in the ischemic hindlimb.

    PubMed

    Lohr, Nicole L; Ninomiya, James T; Warltier, David C; Weihrauch, Dorothée

    2013-09-01

    Nitric oxide (NO) is a crucial mediator of hindlimb collateralization and angiogenesis. Within tissues there are nitrosyl-heme proteins which have the potential to generate NO under conditions of hypoxia or low pH. Low level irradiation of blood and muscle with light in the far red/near infrared spectrum (670 nm, R/NIR) facilitates NO release. Therefore, we assessed the impact of red light exposure on the stimulation of femoral artery collateralization. Rabbits and mice underwent unilateral resection of the femoral artery and chronic R/NIR treatment. The direct NO scavenger carboxy-PTIO and the nitric oxide synthase (NOS) inhibitor L-NAME were also administered in the presence of R/NIR. DAF fluorescence assessed R/NIR changes in NO levels within endothelial cells. In vitro measures of R/NIR induced angiogenesis were assessed by endothelial cell proliferation and migration. R/NIR significantly increased collateral vessel number which could not be attenuated with L-NAME. R/NIR induced collateralization was abolished with c-PTIO. In vitro, NO production increased in endothelial cells with R/NIR exposure, and this finding was independent of NOS inhibition. Similarly R/NIR induced proliferation and tube formation in a NO dependent manner. Finally, nitrite supplementation accelerated R/NIR collateralization in wild type C57Bl/6 mice. In an eNOS deficient transgenic mouse model, R/NIR restores collateral development. In conclusion, R/NIR increases NO levels independent of NOS activity, and leads to the observed enhancement of hindlimb collateralization.

  6. Effects of nifedipine on vascular waterfall and arterial resistance in canine hindlimb.

    PubMed

    Shrier, I; Magder, S

    1995-01-01

    Pressure-flow relations in the canine hindlimb can be well explained by a vascular waterfall at the arteriolar level. Under these conditions, P(art) = Pcrit + Q.Rart, where P(art) is the arterial pressure, Pcrit is the waterfall pressure, Q is regional flow, and Rart is the arterial resistance of the vessels upstream from the waterfall. To determine whether calcium channels in vascular smooth muscle affect Pcrit in addition to Rart, we pump perfused canine hindlimbs and measured both variables over a range of perfusion pressures (Pper) before and during the infusion of the calcium channel blocker nifedipine. Nifedipine significantly decreased Pcrit and Rart at each Pper. Increasing Pper under control conditions from 50 to 150 mmHg significantly increased Pcrit from 24.2 +/- 1.5 to 42.5 +/- 2.2 mmHg. During nifedipine infusion, increasing Pper from 25 to 100 mmHg also increased Pcrit from 14.5 +/- 1.5 to 20.2 +/- 1.9 mmHg, but the rate of increase was less. In contrast to the rise in Pcrit with increasing Pper, Rart significantly decreased from 10.7 +/- 1.1 to 8.1 +/- 1.2 mmHg.min.100 g.ml-1 before nifedipine infusion, and from 5.7 +/- 0.4 to 2.2 +/- 0.1 mmHg.min.100 g.ml-1 during nifedipine infusion. Venous resistance (Rven) significantly decreased with increases in Pper and during nifedipine infusion. The regional elastic recoil pressure (Pel, a measure of small venular pressure) increased with both an increase in Pper and nifedipine. These results suggest that nifedipine decreases Pcrit, Rart, and Rven and that at constant Pper nifedipine increases Pel.

  7. An experimental model of ischemia in rabbit hindlimb.

    PubMed Central

    Hong, J. H.; Bahk, Y. W.; Suh, J. S.; Kwak, B. K.; Shim, H. J.; Kim, J. S.; Kim, H. S.; Moon, Y. H.; Kim, S. J.; Chung, J. W.; Park, J. H.

    2001-01-01

    This study was performed to establish an experimental model of ischemia for the investigation of new treatment modality of limb-threatening ischemia. We produced ischemia in the hindlimbs of 8 New Zealand white rabbits. Under general anesthesia, the left femoral artery was exposed, freed, and excised from distal external iliac artery to proximal popliteal and saphenous arteries. And then both hindlimbs were serially examined to assess the ischemia according to the time table until postoperative 6 weeks. We assessed clinical observation, blood pressure, radioisotopic perfusion scan, and angiography. Clinical ischemic changes of the operated feet were observed in 63%. The blood pressure of left calves was measurable on postoperative day 3 (p<0.05, vs preoperative day 2) and then gradually increased to reach a plateau in postoperative week 6. Radioisotopic arterial perfusion showed similar profiles as in blood pressure. Angiography of ischemic hindlimbs demonstrated a few collateral vessels arising from the internal iliac artery with the reconstitution of the posterior tibial artery in postoperative week 2. In postoperative week 6, collaterals remained the same in number. However, these became dilated and tortuous and showed reconstitution in distal hindleg. In conclusion, this is a reproducible, measurable, and economical animal model of hind limb ischemia. PMID:11641535

  8. Hindlimb unweighting does not alter vasoconstrictor responsiveness and nitric oxide-mediated inhibition of sympathetic vasoconstriction

    PubMed Central

    Just, Timothy P; Jendzjowsky, Nicholas G; DeLorey, Darren S

    2015-01-01

    Abstract We tested the hypothesis that physical inactivity would increase sympathetic vasoconstrictor responsiveness and diminish NO-mediated inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle. Sprague–Dawley rats (n = 33) were randomly assigned to sedentary time control (S) or hindlimb unweighted (HU) groups for 21 days. Following the intervention, rats were anaesthetized and instrumented for measurement of arterial blood pressure and femoral artery blood flow and stimulation of the lumbar sympathetic chain. The percentage change of femoral vascular conductance (%FVC) in response to sympathetic chain stimulation delivered at 2 and 5 Hz was determined at rest and during triceps surae muscle contraction before (control) and after NO synthase blockade with l-NAME (5 mg kg i.v.). Sympathetic vasoconstrictor responsiveness was not different (P > 0.05) in S and HU rats at rest (S, 2 Hz, −26 ± 8% and 5 Hz, −46 ± 12%; and HU, 2 Hz, −29 ± 9% and 5 Hz, −51 ± 10%) and during contraction (S, 2 Hz, −10 ± 7% and 5 Hz, −23 ± 11%; and HU, 2 Hz, −9 ± 5% and 5 Hz, −22 ± 7%). Nitric oxide synthase blockade caused a similar increase (P > 0.05) in sympathetic vasoconstrictor responsiveness in HU and S rats at rest (S, 2 Hz, −41 ± 7% and 5 Hz, −58 ± 8%; and HU, 2 Hz, −43 ± 6% and 5 Hz, −63 ± 8%) and during muscle contraction (S, 2 Hz, −15 ± 6% and 5 Hz, −31 ± 11%; and HU, 2 Hz, −12 ± 5% and 5 Hz, −29 ± 8%). Skeletal muscle NO synthase expression and ACh-mediated vasodilatation were also not different between HU and S rats. These data suggest that HU does not alter sympathetic vasoconstrictor responsiveness and NO-mediated inhibition of sympathetic vasoconstriction in resting and contracting skeletal muscle. Key points Physical inactivity increases the risk of cardiovascular disease and may alter sympathetic nervous system control of vascular

  9. Misexpression experiment of Tbx5 in axolotl (Ambystoma mexicanum) hindlimb blastema.

    PubMed

    Shimokawa, Takashi; Kominami, Rieko; Yasutaka, Satoru; Shinohara, Harumichi

    2013-01-01

    Axolotls (Ambystoma mexicanum) have the ability to regenerate amputated limbs throughout their life span. In the present study, we attempted to elucidate how axolotls can specify limb type correctly during the regeneration process. We misexpressed Tbx5 in regenerating hindlimb blastema, and consequently a forelimb-like hindlimb regenerated from the hindlimb blastema. On the other hand, no change was observed in Tbx5-overexpressing forelimb blastema, and thus we considered that Tbx5 plays a key role in the specification of forelimb during the regeneration process of axolotl limbs. However, axolotls' fore- and hindlimbs have very similar structures except for the number of fingers, and it was very difficult to judge whether the forelimb-like regenerate was a true forelimb or merely a forelimb-like hindlimb. Therefore, in order to confirm our conclusion, we have to investigate other genes that are expressed differentially between fore- and hindlimbs in future experiments.

  10. Basal glycogenolysis in mouse skeletal muscle: in vitro model predicts in vivo fluxes

    NASA Technical Reports Server (NTRS)

    Lambeth, Melissa J.; Kushmerick, Martin J.; Marcinek, David J.; Conley, Kevin E.

    2002-01-01

    A previously published mammalian kinetic model of skeletal muscle glycogenolysis, consisting of literature in vitro parameters, was modified by substituting mouse specific Vmax values. The model demonstrates that glycogen breakdown to lactate is under ATPase control. Our criteria to test whether in vitro parameters could reproduce in vivo dynamics was the ability of the model to fit phosphocreatine (PCr) and inorganic phosphate (Pi) dynamic NMR data from ischemic basal mouse hindlimbs and predict biochemically-assayed lactate concentrations. Fitting was accomplished by optimizing four parameters--the ATPase rate coefficient, fraction of activated glycogen phosphorylase, and the equilibrium constants of creatine kinase and adenylate kinase (due to the absence of pH in the model). The optimized parameter values were physiologically reasonable, the resultant model fit the [PCr] and [Pi] timecourses well, and the model predicted the final measured lactate concentration. This result demonstrates that additional features of in vivo enzyme binding are not necessary for quantitative description of glycogenolytic dynamics.

  11. Computational model of cellular metabolic dynamics: effect of insulin on glucose disposal in human skeletal muscle

    PubMed Central

    Li, Yanjun; Solomon, Thomas P. J.; Haus, Jacob M.; Saidel, Gerald M.; Cabrera, Marco E.

    2010-01-01

    Identifying the mechanisms by which insulin regulates glucose metabolism in skeletal muscle is critical to understanding the etiology of insulin resistance and type 2 diabetes. Our knowledge of these mechanisms is limited by the difficulty of obtaining in vivo intracellular data. To quantitatively distinguish significant transport and metabolic mechanisms from limited experimental data, we developed a physiologically based, multiscale mathematical model of cellular metabolic dynamics in skeletal muscle. The model describes mass transport and metabolic processes including distinctive processes of the cytosol and mitochondria. The model simulated skeletal muscle metabolic responses to insulin corresponding to human hyperinsulinemic-euglycemic clamp studies. Insulin-mediated rate of glucose disposal was the primary model input. For model validation, simulations were compared with experimental data: intracellular metabolite concentrations and patterns of glucose disposal. Model variations were simulated to investigate three alternative mechanisms to explain insulin enhancements: Model 1 (M.1), simple mass action; M.2, insulin-mediated activation of key metabolic enzymes (i.e., hexokinase, glycogen synthase, pyruvate dehydrogenase); or M.3, parallel activation by a phenomenological insulin-mediated intracellular signal that modifies reaction rate coefficients. These simulations indicated that models M.1 and M.2 were not sufficient to explain the experimentally measured metabolic responses. However, by application of mechanism M.3, the model predicts metabolite concentration changes and glucose partitioning patterns consistent with experimental data. The reaction rate fluxes quantified by this detailed model of insulin/glucose metabolism provide information that can be used to evaluate the development of type 2 diabetes. PMID:20332360

  12. Interstitial and arterial–venous [K+] in human calf muscle during dynamic exercise: effect of ischaemia and relation to muscle pain

    PubMed Central

    Green, Simon; Langberg, Henning; Skovgaard, Dorthe; Bülow, Jens; Kjær, Michael

    2000-01-01

    Changes in the concentration of interstitial K+ surrounding skeletal muscle fibres ([K+]I) probably play some role in the regulation of cardiovascular adjustments to muscular activity, as well as in the aetiology of muscle pain and fatigue during high-intensity exercise. However, there is very little information on the response of [K+]I to exercise in human skeletal muscle. Five young healthy subjects performed plantar flexion exercise for four 5 min periods at increasing power outputs (∼1–6 W) with 10 min intervening recovery periods, as well as for two 5 min periods with ischaemia at ∼1 and ∼3 W. Microdialysis probes were inserted into the gastrocnemius medialis muscle of the right leg to measure [K+]I, and K+ release from the plantar flexors during and after incremental exercise was calculated from plasma flow and arterial–venous differences for K+. Calf muscle pain was assessed using a visual analogue scale. On average, [K+]I was 4.4 mmol l−1 at rest and increased during minutes 3–5 of incremental exercise by ∼1–7 mmol l−1 as a positive function of power output. K+ release also increased as a function of exercise intensity, although there was a progressive increase by ∼1–6 mmol l−1 in the [K+] gradient between the interstitium and arterial–venous plasma. [K+]I was lower during ischaemic exercise than control exercise. In contrast to this effect of ischaemia on [K+]I, muscle pain was relatively higher during ischaemic exercise, which demonstrates that factors other than changes in [K+]I are responsible for ischaemic muscle pain. In conclusion, this study has demonstrated that during 5 min of dynamic exercise, [K+]I increases during the later period of exercise as a positive function of exercise intensity, ischaemia reduces [K+]I during rest and exercise, and the increase in [K+]I is not responsible for muscle pain during ischaemic exercise. PMID:11118511

  13. Eldecalcitol improves muscle strength and dynamic balance in postmenopausal women with osteoporosis: an open-label randomized controlled study.

    PubMed

    Saito, Kimio; Miyakoshi, Naohisa; Matsunaga, Toshiki; Hongo, Michio; Kasukawa, Yuji; Shimada, Yoichi

    2016-09-01

    The antifracture efficacy of vitamin D in osteoporosis is due to its direct action on bones and indirect extraskeletal effects to prevent falls. Eldecalcitol is an analog of active vitamin D3 that improves bone mineral density and reduces the risk of osteoporotic fractures. However, the effects of eldecalcitol on muscle strength and static and dynamic postural balance are unclear. In this open-label randomized controlled study, we assessed the effects of eldecalcitol on muscle strength and static and dynamic postural balance in 50 postmenopausal women (mean age 74 years) with osteoporosis treated with bisphosphonate. Participants were randomly divided into a bisphosphonate group (alendronate at 35 mg/week; n = 25) or an eldecalcitol group (eldecalcitol at 0.75 μg/day and alendronate at 35 mg/week; n = 25) and were followed up for 6 months. Trunk muscle strength, including back extensor strength and iliopsoas muscle strength, was measured. Static standing balance was evaluated and the one leg standing test was performed to assess static postural balance. Dynamic sitting balance was evaluated and the 10-m walk test, functional reach test, and timed up and go test were performed to assess dynamic postural balance. At 6 months, there were no significant changes in any measure of muscle strength or balance in the bisphosphonate group, whereas eldecalcitol significantly increased back extensor strength (p = 0.012) and iliopsoas muscle strength (p = 0.035). Eldecalcitol also significantly improved findings on the timed up and go test (p = 0.001) and dynamic sitting balance (p = 0.015) at 6 months. These results with eldecalcitol may have an impact on prevention of falls.

  14. Trans-illuminated laser speckle imaging of collateral artery blood flow in ischemic mouse hindlimb

    PubMed Central

    Meisner, Joshua K.; Niu, Jacqueline; Sumer, Suna

    2013-01-01

    Abstract. The mouse ischemic hindlimb model is used widely for studying collateral artery growth (i.e., arteriogenesis) in response to increased shear stress. Nonetheless, precise measurements of regional shear stress changes along individual collateral arteries are lacking. Our goal is to develop and verify trans-illumination laser speckle flowmetry (LSF) for this purpose. Studies of defibrinated bovine blood flow through tubes embedded in tissue-mimicking phantoms indicate that trans-illumination LSF better maintains sensitivity with an increasing tissue depth when compared to epi-illumination, with an ∼50% reduction in the exponential decay of the speckle velocity signal. Applying trans-illuminated LSF to the gracilis muscle collateral artery network in vivo yields both improved sensitivity and reduced noise when compared to epi-illumination. Trans-illuminated LSF images reveal regional differences in collateral artery blood velocity after femoral artery ligation and are used to measure an ∼2-fold increase in the shear stress at the entrance regions to the muscle. We believe these represent the first direct measurements of regional shear stress changes in individual mouse collateral arteries. The ability to capture deeper vascular signals using a trans-illumination configuration for LSF may expand the current applications for LSF, which could have bearing on determining how shear stress magnitude and direction regulate arteriogenesis. PMID:24045691

  15. Hyperpolarized functional magnetic resonance of murine skeletal muscle enabled by multiple tracer-paradigm synchronizations.

    PubMed

    Leftin, Avigdor; Roussel, Tangi; Frydman, Lucio

    2014-01-01

    Measuring metabolism's time- and space-dependent responses upon stimulation lies at the core of functional magnetic resonance imaging. While focusing on water's sole resonance, further insight could arise from monitoring the temporal responses arising from the metabolites themselves, in what is known as functional magnetic resonance spectroscopy. Performing these measurements in real time, however, is severely challenged by the short functional timescales and low concentrations of natural metabolites. Dissolution dynamic nuclear polarization is an emerging technique that can potentially alleviate this, as it provides a massive sensitivity enhancement allowing one to probe low-concentration tracers and products in a single-scan. Still, conventional implementations of this hyperpolarization approach are not immediately amenable to the repeated acquisitions needed in real-time functional settings. This work proposes a strategy for functional magnetic resonance of hyperpolarized metabolites that bypasses this limitation, and enables the observation of real-time metabolic changes through the synchronization of stimuli-triggered, multiple-bolus injections of the metabolic tracer 13C1-pyruvate. This new approach is demonstrated with paradigms tailored to reveal in vivo thresholds of murine hind-limb skeletal muscle activation, involving the conversion of 13C1-pyruvate to 13C1-lactate and 13C1-alanine. These functional hind-limb studies revealed that graded skeletal muscle stimulation causes commensurate increases in glycolytic metabolism in a frequency- and amplitude-dependent fashion, that can be monitored on the seconds/minutes timescale using dissolution dynamic nuclear polarization. Spectroscopic imaging further allowed the in vivo visualization of uptake, transformation and distribution of the tracer and products, in fast-twitch glycolytic and in slow-twitch oxidative muscle fiber groups. While these studies open vistas in time and sensitivity for metabolic

  16. Hyperpolarized Functional Magnetic Resonance of Murine Skeletal Muscle Enabled by Multiple Tracer-Paradigm Synchronizations

    PubMed Central

    Leftin, Avigdor; Roussel, Tangi; Frydman, Lucio

    2014-01-01

    Measuring metabolism's time- and space-dependent responses upon stimulation lies at the core of functional magnetic resonance imaging. While focusing on water's sole resonance, further insight could arise from monitoring the temporal responses arising from the metabolites themselves, in what is known as functional magnetic resonance spectroscopy. Performing these measurements in real time, however, is severely challenged by the short functional timescales and low concentrations of natural metabolites. Dissolution dynamic nuclear polarization is an emerging technique that can potentially alleviate this, as it provides a massive sensitivity enhancement allowing one to probe low-concentration tracers and products in a single-scan. Still, conventional implementations of this hyperpolarization approach are not immediately amenable to the repeated acquisitions needed in real-time functional settings. This work proposes a strategy for functional magnetic resonance of hyperpolarized metabolites that bypasses this limitation, and enables the observation of real-time metabolic changes through the synchronization of stimuli-triggered, multiple-bolus injections of the metabolic tracer 13C1-pyruvate. This new approach is demonstrated with paradigms tailored to reveal in vivo thresholds of murine hind-limb skeletal muscle activation, involving the conversion of 13C1-pyruvate to 13C1-lactate and 13C1-alanine. These functional hind-limb studies revealed that graded skeletal muscle stimulation causes commensurate increases in glycolytic metabolism in a frequency- and amplitude-dependent fashion, that can be monitored on the seconds/minutes timescale using dissolution dynamic nuclear polarization. Spectroscopic imaging further allowed the in vivo visualization of uptake, transformation and distribution of the tracer and products, in fast-twitch glycolytic and in slow-twitch oxidative muscle fiber groups. While these studies open vistas in time and sensitivity for metabolic

  17. Hindlimb unweighting decreases endothelium-dependent dilation and eNOS expression in soleus not gastrocnemius

    NASA Technical Reports Server (NTRS)

    Woodman, C. R.; Schrage, W. G.; Rush, J. W.; Ray, C. A.; Price, E. M.; Hasser, E. M.; Laughlin, M. H.

    2001-01-01

    We tested the hypothesis that hindlimb unweighting (HLU) decreases endothelium-dependent vasodilation and expression of endothelial nitric oxide synthase (eNOS) and superoxide dismutase-1 (SOD-1) in arteries of skeletal muscle with reduced blood flow during HLU. Sprague-Dawley rats (300-350 g) were exposed to HLU (n = 15) or control (n = 15) conditions for 14 days. ACh-induced dilation was assessed in muscle with reduced [soleus (Sol)] or unchanged [gastrocnemius (Gast)] blood flow during HLU. eNOS and SOD-1 expression were measured in feed arteries (FA) and in first-order (1A), second-order (2A), and third-order (3A) arterioles. Dilation to infusion of ACh in vivo was blunted in Sol but not Gast. In arteries of Sol muscle, HLU decreased eNOS mRNA and protein content. eNOS mRNA content was significantly less in Sol FA (35%), 1A arterioles (25%) and 2A arterioles (18%). eNOS protein content was less in Sol FA (64%) and 1A arterioles (65%) from HLU rats. In arteries of Gast, HLU did not decrease eNOS mRNA or protein. SOD-1 mRNA expression was less in Sol 2A arterioles (31%) and 3A arterioles (29%) of HLU rats. SOD-1 protein content was less in Sol FA (67%) but not arterioles. SOD-1 mRNA and protein content were not decreased in arteries from Gast. These data indicate that HLU decreases endothelium-dependent vasodilation, eNOS expression, and SOD-1 expression primarily in arteries of Sol muscle where blood flow is reduced during HLU.

  18. Computational Intelligence Based Data Fusion Algorithm for Dynamic sEMG and Skeletal Muscle Force Modelling

    SciTech Connect

    Chandrasekhar Potluri,; Madhavi Anugolu; Marco P. Schoen; D. Subbaram Naidu

    2013-08-01

    In this work, an array of three surface Electrography (sEMG) sensors are used to acquired muscle extension and contraction signals for 18 healthy test subjects. The skeletal muscle force is estimated using the acquired sEMG signals and a Non-linear Wiener Hammerstein model, relating the two signals in a dynamic fashion. The model is obtained from using System Identification (SI) algorithm. The obtained force models for each sensor are fused using a proposed fuzzy logic concept with the intent to improve the force estimation accuracy and resilience to sensor failure or misalignment. For the fuzzy logic inference system, the sEMG entropy, the relative error, and the correlation of the force signals are considered for defining the membership functions. The proposed fusion algorithm yields an average of 92.49% correlation between the actual force and the overall estimated force output. In addition, the proposed fusionbased approach is implemented on a test platform. Experiments indicate an improvement in finger/hand force estimation.

  19. Development and evolution of the muscles of the pelvic fin.

    PubMed

    Cole, Nicholas J; Hall, Thomas E; Don, Emily K; Berger, Silke; Boisvert, Catherine A; Neyt, Christine; Ericsson, Rolf; Joss, Jean; Gurevich, David B; Currie, Peter D

    2011-10-01

    Locomotor strategies in terrestrial tetrapods have evolved from the utilisation of sinusoidal contractions of axial musculature, evident in ancestral fish species, to the reliance on powerful and complex limb muscles to provide propulsive force. Within tetrapods, a hindlimb-dominant locomotor strategy predominates, and its evolution is considered critical for the evident success of the tetrapod transition onto land. Here, we determine the developmental mechanisms of pelvic fin muscle formation in living fish species at critical points within the vertebrate phylogeny and reveal a stepwise modification from a primitive to a more derived mode of pelvic fin muscle formation. A distinct process generates pelvic fin muscle in bony fishes that incorporates both primitive and derived characteristics of vertebrate appendicular muscle formation. We propose that the adoption of the fully derived mode of hindlimb muscle formation from this bimodal character state is an evolutionary innovation that was critical to the success of the tetrapod transition.

  20. Development and Evolution of the Muscles of the Pelvic Fin

    PubMed Central

    Cole, Nicholas J.; Hall, Thomas E.; Don, Emily K.; Berger, Silke; Boisvert, Catherine A.; Neyt, Christine; Ericsson, Rolf; Joss, Jean; Gurevich, David B.; Currie, Peter D.

    2011-01-01

    Locomotor strategies in terrestrial tetrapods have evolved from the utilisation of sinusoidal contractions of axial musculature, evident in ancestral fish species, to the reliance on powerful and complex limb muscles to provide propulsive force. Within tetrapods, a hindlimb-dominant locomotor strategy predominates, and its evolution is considered critical for the evident success of the tetrapod transition onto land. Here, we determine the developmental mechanisms of pelvic fin muscle formation in living fish species at critical points within the vertebrate phylogeny and reveal a stepwise modification from a primitive to a more derived mode of pelvic fin muscle formation. A distinct process generates pelvic fin muscle in bony fishes that incorporates both primitive and derived characteristics of vertebrate appendicular muscle formation. We propose that the adoption of the fully derived mode of hindlimb muscle formation from this bimodal character state is an evolutionary innovation that was critical to the success of the tetrapod transition. PMID:21990962

  1. Development and evolution of the muscles of the pelvic fin.

    PubMed

    Cole, Nicholas J; Hall, Thomas E; Don, Emily K; Berger, Silke; Boisvert, Catherine A; Neyt, Christine; Ericsson, Rolf; Joss, Jean; Gurevich, David B; Currie, Peter D

    2011-10-01

    Locomotor strategies in terrestrial tetrapods have evolved from the utilisation of sinusoidal contractions of axial musculature, evident in ancestral fish species, to the reliance on powerful and complex limb muscles to provide propulsive force. Within tetrapods, a hindlimb-dominant locomotor strategy predominates, and its evolution is considered critical for the evident success of the tetrapod transition onto land. Here, we determine the developmental mechanisms of pelvic fin muscle formation in living fish species at critical points within the vertebrate phylogeny and reveal a stepwise modification from a primitive to a more derived mode of pelvic fin muscle formation. A distinct process generates pelvic fin muscle in bony fishes that incorporates both primitive and derived characteristics of vertebrate appendicular muscle formation. We propose that the adoption of the fully derived mode of hindlimb muscle formation from this bimodal character state is an evolutionary innovation that was critical to the success of the tetrapod transition. PMID:21990962

  2. In vivo dynamics of skeletal muscle Dystrophin in zebrafish embryos revealed by improved FRAP analysis

    PubMed Central

    Bajanca, Fernanda; Gonzalez-Perez, Vinicio; Gillespie, Sean J; Beley, Cyriaque; Garcia, Luis; Theveneau, Eric; Sear, Richard P; Hughes, Simon M

    2015-01-01

    Dystrophin forms an essential link between sarcolemma and cytoskeleton, perturbation of which causes muscular dystrophy. We analysed Dystrophin binding dynamics in vivo for the first time. Within maturing fibres of host zebrafish embryos, our analysis reveals a pool of diffusible Dystrophin and complexes bound at the fibre membrane. Combining modelling, an improved FRAP methodology and direct semi-quantitative analysis of bleaching suggests the existence of two membrane-bound Dystrophin populations with widely differing bound lifetimes: a stable, tightly bound pool, and a dynamic bound pool with high turnover rate that exchanges with the cytoplasmic pool. The three populations were found consistently in human and zebrafish Dystrophins overexpressed in wild-type or dmdta222a/ta222a zebrafish embryos, which lack Dystrophin, and in Gt(dmd-Citrine)ct90a that express endogenously-driven tagged zebrafish Dystrophin. These results lead to a new model for Dystrophin membrane association in developing muscle, and highlight our methodology as a valuable strategy for in vivo analysis of complex protein dynamics. DOI: http://dx.doi.org/10.7554/eLife.06541.001 PMID:26459831

  3. Bioinformatics Analysis of Transcriptome Dynamics During Growth in Angus Cattle Longissimus Muscle

    PubMed Central

    Moisá, Sonia J.; Shike, Daniel W.; Graugnard, Daniel E.; Rodriguez-Zas, Sandra L.; Everts, Robin E.; Lewin, Harris A.; Faulkner, Dan B.; Berger, Larry L.; Loor, Juan J.

    2013-01-01

    Transcriptome dynamics in the longissimus muscle (LM) of young Angus cattle were evaluated at 0, 60, 120, and 220 days from early-weaning. Bioinformatic analysis was performed using the dynamic impact approach (DIA) by means of Kyoto Encyclopedia of Genes and Genomes (KEGG) and Database for Annotation, Visualization and Integrated Discovery (DAVID) databases. Between 0 to 120 days (growing phase) most of the highly-impacted pathways (eg, ascorbate and aldarate metabolism, drug metabolism, cytochrome P450 and Retinol metabolism) were inhibited. The phase between 120 to 220 days (finishing phase) was characterized by the most striking differences with 3,784 differentially expressed genes (DEGs). Analysis of those DEGs revealed that the most impacted KEGG canonical pathway was glycosylphosphatidylinositol (GPI)-anchor biosynthesis, which was inhibited. Furthermore, inhibition of calpastatin and activation of tyrosine aminotransferase ubiquitination at 220 days promotes proteasomal degradation, while the concurrent activation of ribosomal proteins promotes protein synthesis. Therefore, the balance of these processes likely results in a steady-state of protein turnover during the finishing phase. Results underscore the importance of transcriptome dynamics in LM during growth. PMID:23943656

  4. Acute effects of blood flow restriction on muscle activity and endurance during fatiguing dynamic knee extensions at low load.

    PubMed

    Wernbom, Mathias; Järrebring, Rickard; Andreasson, Mikael A; Augustsson, Jesper

    2009-11-01

    The purpose of this study was to investigate muscle activity and endurance during fatiguing low-intensity dynamic knee extension exercise with and without blood flow restriction. Eleven healthy subjects with strength training experience performed 3 sets of unilateral knee extensions with no relaxation between repetitions to concentric torque failure at 30% of the 1 repetition maximum. One leg was randomized to exercise with cuff occlusion and the other leg to exercise without occlusion. The muscle activity in the quadriceps was recorded with electromyography (EMG). Ratings of perceived exertion (RPE) and acute pain were collected immediately, and delayed onset muscle soreness (DOMS) was rated before and at 24, 48, and 72 hours after exercise. The results demonstrated high EMG levels in both experimental conditions, but there were no significant differences regarding maximal muscle activity, except for a higher EMG in the eccentric phase in set 3 for the nonoccluded condition (p = 0.005). Significantly more repetitions were performed with the nonoccluded leg in every set (p < 0.05). The RPE and acute pain ratings were similar, but DOMS was higher in the nonoccluded leg (p < 0.05). We conclude that blood flow restriction during low-intensity dynamic knee extension decreases the endurance but does not increase the maximum muscle activity compared with training without restriction when both regimes are performed to failure. The high levels of muscle activity suggest that performing low-load dynamic knee extensions in a no-relaxation manner may be a useful method in knee rehabilitation settings when large forces are contraindicated. However, similarly to fatiguing blood flow restricted exercise, this method is associated with ischemic muscle pain, and thus its applications may be limited to highly motivated individuals.

  5. Orexin system is expressed in avian muscle cells and regulates mitochondrial dynamics.

    PubMed

    Lassiter, Kentu; Greene, Elizabeth; Piekarski, Alissa; Faulkner, Olivia B; Hargis, Billy M; Bottje, Walter; Dridi, Sami

    2015-02-01

    Orexin A and B, orexigenic peptides produced primarily by the lateral hypothalamus that signal through two G protein-coupled receptors, orexin receptors 1/2, have been implicated in the regulation of several physiological processes in mammals. In avian (nonmammalian vertebrates) species; however, the physiological roles of orexin are not well defined. Here, we provide novel evidence that not only is orexin and its related receptors 1/2 (ORXR1/2) expressed in chicken muscle tissue and quail muscle (QM7) cell line, orexin appears to be a secretory protein in QM7 cells. In vitro administration of recombinant orexin A and B (rORX-A and B) differentially regulated prepro-orexin expression in a dose-dependent manner with up-regulation for rORX-A (P < 0.05) and downregulation for rORX-B (P < 0.05) in QM7 cells. While both peptides upregulated ORXR1 expression, only a high dose of rORX-B decreased the expression of ORXR2 (P < 0.05). The presence of orexin and its related receptors and the regulation of its own system in avian muscle cells indicate that orexin may have autocrine, paracrine, and/or endocrine roles. rORXs differentially regulated mitochondrial dynamics network. While rORX-A significantly induced the expression of mitochondrial fission-related genes (DNM1, MTFP1, MTFR1), rORX-B increased the expression of mitofusin 2, OPA1, and OMA1 genes that are involved in mitochondrial fusion. Concomitant with these changes, rORXs differentially regulated the expression of several mitochondrial metabolic genes (av-UCP, av-ANT, Ski, and NRF-1) and their related transcriptional regulators (PPARγ, PPARα, PGC-1α, PGC-1β, and FoxO-1) without affecting ATP synthesis. Taken together, our data represent the first evidence of the presence and secretion of orexin system in the muscle of nonmammalian species and its role in mitochondrial fusion and fission, probably through mitochondrial-related genes and their related transcription factors.

  6. Effectiveness of core muscle strengthening for improving pain and dynamic balance among female patients with patellofemoral pain syndrome.

    PubMed

    Chevidikunnan, Mohamed Faisal; Al Saif, Amer; Gaowgzeh, Riziq Allah; Mamdouh, Khaled A

    2016-05-01

    [Purpose] Patellofemoral pain syndrome is a frequent musculoskeletal disorder, which can result from core muscles instability that can lead to pain and altered dynamic balance. The objective of this study is to assess the effect of core muscle strengthening on pain and dynamic balance in female patients with patellofemoral pain syndrome. [Subjects and Methods] Twenty female patients with age ranging from 16 to 40 years with patellofemoral pain syndrome were divided into study (N=10) and control (N=10) groups. Both groups were given 4 weeks of conventional physical therapy program and an additional core muscle strengthening for the study group. The tools used to assess the outcome were Visual Analogue Scale and Star Excursion Balance Test. [Results] The results of the study show that participants in the study group revealed a significantly greater improvement in the intensity of pain and dynamic balance as compared to the control group. [Conclusion] Adding a core muscle-strengthening program to the conventional physical therapy management improves pain and dynamic balance in female patients with patellofemoral pain syndrome. PMID:27313363

  7. Effectiveness of core muscle strengthening for improving pain and dynamic balance among female patients with patellofemoral pain syndrome

    PubMed Central

    Chevidikunnan, Mohamed Faisal; Al Saif, Amer; Gaowgzeh, Riziq Allah; Mamdouh, Khaled A

    2016-01-01

    [Purpose] Patellofemoral pain syndrome is a frequent musculoskeletal disorder, which can result from core muscles instability that can lead to pain and altered dynamic balance. The objective of this study is to assess the effect of core muscle strengthening on pain and dynamic balance in female patients with patellofemoral pain syndrome. [Subjects and Methods] Twenty female patients with age ranging from 16 to 40 years with patellofemoral pain syndrome were divided into study (N=10) and control (N=10) groups. Both groups were given 4 weeks of conventional physical therapy program and an additional core muscle strengthening for the study group. The tools used to assess the outcome were Visual Analogue Scale and Star Excursion Balance Test. [Results] The results of the study show that participants in the study group revealed a significantly greater improvement in the intensity of pain and dynamic balance as compared to the control group. [Conclusion] Adding a core muscle-strengthening program to the conventional physical therapy management improves pain and dynamic balance in female patients with patellofemoral pain syndrome. PMID:27313363

  8. Trunk muscle coactivation is tuned to changes in task dynamics to improve responsiveness in a seated balance task.

    PubMed

    Oomen, Nathalie M C W; Reeves, N Peter; Priess, M Cody; van Dieën, Jaap H

    2015-10-01

    When balancing, instability can occur when the object being balanced moves at a rate that is beyond the abilities of human motor control. This illustrates that responsiveness of motor control is limited and can be investigated by changing the dynamics of the task. In this study, the responsiveness of trunk motor control was investigated by changing the seat stiffness of an unstable seat. At decreasing levels of seat stiffness the probability of successfully balancing on the seat, speed of the seat, speed of the trunk relative to the seat (trunk-seat) and muscle activation of five trunk muscles were assessed. Also, across the different stiffness levels, the relation between trunk muscle activation and seat speed was determined. As hypothesized, with decreasing seat stiffness the probability of success decreased, seat speed and trunk-seat speed increased, and both agonist and antagonist activation increased. This shows that limits in the responsiveness of trunk motor control were reached during seated balancing. Furthermore, in line with our hypothesis, a positive relation was found between trunk muscle activation and seat speed. It appears that the central nervous system regulates trunk stiffness (via muscle coactivation) in relation to the dynamics of the task, possibly to maintain adequate responsiveness.

  9. Glucagon-like peptide-1 inhibits vascular smooth muscle cell dedifferentiation through mitochondrial dynamics regulation.

    PubMed

    Torres, Gloria; Morales, Pablo E; García-Miguel, Marina; Norambuena-Soto, Ignacio; Cartes-Saavedra, Benjamín; Vidal-Peña, Gonzalo; Moncada-Ruff, David; Sanhueza-Olivares, Fernanda; San Martín, Alejandra; Chiong, Mario

    2016-03-15

    Glucagon-like peptide-1 (GLP-1) is a neuroendocrine hormone produced by gastrointestinal tract in response to food ingestion. GLP-1 plays a very important role in the glucose homeostasis by stimulating glucose-dependent insulin secretion, inhibiting glucagon secretion, inhibiting gastric emptying, reducing appetite and food intake. Because of these actions, the GLP-1 peptide-mimetic exenatide is one of the most promising new medicines for the treatment of type 2 diabetes. In vivo treatments with GLP-1 or exenatide prevent neo-intima layer formation in response to endothelial damage and atherosclerotic lesion formation in aortic tissue. Whether GLP-1 modulates vascular smooth muscle cell (VSMC) migration and proliferation by controlling mitochondrial dynamics is unknown. In this report, we showed that GLP-1 increased mitochondrial fusion and activity in a PKA-dependent manner in the VSMC cell line A7r5. GLP-1 induced a Ser-637 phosphorylation in the mitochondrial fission protein Drp1, and decreased Drp1 mitochondrial localization. GLP-1 inhibited PDGF-BB-induced VSMC migration and proliferation, actions inhibited by overexpressing wild type Drp1 and mimicked by the Drp1 inhibitor Mdivi-1 and by overexpressing dominant negative Drp1. These results show that GLP-1 stimulates mitochondrial fusion, increases mitochondrial activity and decreases PDGF-BB-induced VSMC dedifferentiation by a PKA/Drp1 signaling pathway. Our data suggest that GLP-1 inhibits vascular remodeling through a mitochondrial dynamics-dependent mechanism.

  10. Glucagon-like peptide-1 inhibits vascular smooth muscle cell dedifferentiation through mitochondrial dynamics regulation.

    PubMed

    Torres, Gloria; Morales, Pablo E; García-Miguel, Marina; Norambuena-Soto, Ignacio; Cartes-Saavedra, Benjamín; Vidal-Peña, Gonzalo; Moncada-Ruff, David; Sanhueza-Olivares, Fernanda; San Martín, Alejandra; Chiong, Mario

    2016-03-15

    Glucagon-like peptide-1 (GLP-1) is a neuroendocrine hormone produced by gastrointestinal tract in response to food ingestion. GLP-1 plays a very important role in the glucose homeostasis by stimulating glucose-dependent insulin secretion, inhibiting glucagon secretion, inhibiting gastric emptying, reducing appetite and food intake. Because of these actions, the GLP-1 peptide-mimetic exenatide is one of the most promising new medicines for the treatment of type 2 diabetes. In vivo treatments with GLP-1 or exenatide prevent neo-intima layer formation in response to endothelial damage and atherosclerotic lesion formation in aortic tissue. Whether GLP-1 modulates vascular smooth muscle cell (VSMC) migration and proliferation by controlling mitochondrial dynamics is unknown. In this report, we showed that GLP-1 increased mitochondrial fusion and activity in a PKA-dependent manner in the VSMC cell line A7r5. GLP-1 induced a Ser-637 phosphorylation in the mitochondrial fission protein Drp1, and decreased Drp1 mitochondrial localization. GLP-1 inhibited PDGF-BB-induced VSMC migration and proliferation, actions inhibited by overexpressing wild type Drp1 and mimicked by the Drp1 inhibitor Mdivi-1 and by overexpressing dominant negative Drp1. These results show that GLP-1 stimulates mitochondrial fusion, increases mitochondrial activity and decreases PDGF-BB-induced VSMC dedifferentiation by a PKA/Drp1 signaling pathway. Our data suggest that GLP-1 inhibits vascular remodeling through a mitochondrial dynamics-dependent mechanism. PMID:26807480

  11. Forward dynamics simulations provide insight into muscle mechanical work during human locomotion.

    PubMed

    Neptune, Richard R; McGowan, Craig P; Kautz, Steven A

    2009-10-01

    Complex musculoskeletal models and computer simulations can provide critical insight into muscle mechanical work output during locomotion. Simulations provide both a consistent mechanical solution that can be interrogated at multiple levels (muscle fiber, musculotendon, net joint moment, and whole-body work) and an ideal framework to identify limitations with different estimates of muscle work and the resulting implications for metabolic cost and efficiency.

  12. Effect of caffeine and ethanolic extract of kolanut on glucose uptake in the canine hindlimb at rest and during contraction.

    PubMed

    Salahdeen, H M; Alada, A R A

    2009-06-01

    The study investigated the effects of caffeine and ethanolic extract of kolanut (EEK) on glucose uptake in the canine hindlimb at rest and during contraction. Thirty male anaesthetized mongrel dogs [11-13 kg] were divided into six groups [5 dogs/group] Caffeine [6 mg/kg], EEK [5 mg/kg], or normal saline [control] was administered intravenously to each group at rest. Arterial and venous blood samples were collected at 0, 5, 10, 15, 20, 25, 30, 45, 60, 75 and 90 minutes after drug administration. Blood glucose was measured by glucose oxidase method. Arteriovenous [A-V] glucose difference was calculated and venous blood flow [VBF] was measured during the sampling period. Hindlimb glucose uptake [HGU] was calculated as the product of [A-V] glucose and blood flow. After sampling at rest, the experiments were repeated with the right femoral nerve stimulated using electrical stimulator at 5 Hz. At rest, A-V glucose increased significantly [P<0.05] from 4.2+/-0.2 mg/dl to 29.8+/-8.6, and 24.4+/-2.6 for caffeine and EEK respectively. VBF decreased to 2.0+/-0.9 and 6.0+/-0.6 ml/min for caffeine and EEK respectively. However, HGU significantly increased from 34.8+/-0.1 mg/min to 74.5+/-3.2 mg/min and 175.8+/-3.4 mg/min for caffeine and EEK, respectively. Contraction of the hindlimb muscle alone significantly increased the [A-V] glucose [68%], VBF [26%] and HGU [120%] when compared with the control. During contraction, [A-V] glucose increased from 4.3 +/-1.5 mg/dl to 35.6+/-3.0 mg/dl, and 27.0+/-2.2 mg/dl for caffeine and EEK respectively. VBF also increased from 8.4+/-0.3 ml/min to 12.8+/-0.3 ml/min for EEK. Although, contraction improves VBF [7.3+/-0.5 ml/min] to the hindlimb in response to caffeine, the value was significantly [P<0.05] lower than that of control [8.4+/-0.5 ml/min]. Contraction also significantly increased HGU from 35.8+/-3.6 mg/min to 249.0+/-3.3 and 286.72+/-2.0 mg/min for caffeine and EEK, respectively. The results showed that caffeine and EEK

  13. Intermuscular adipose tissue and thigh muscle area dynamics during an 18-month randomized weight loss trial.

    PubMed

    Yaskolka Meir, Anat; Shelef, Ilan; Schwarzfuchs, Dan; Gepner, Yftach; Tene, Lilac; Zelicha, Hila; Tsaban, Gal; Bilitzky, Avital; Komy, Oded; Cohen, Noa; Bril, Nitzan; Rein, Michal; Serfaty, Dana; Kenigsbuch, Shira; Chassidim, Yoash; Zeller, Lior; Ceglarek, Uta; Stumvoll, Michael; Blüher, Matthias; Thiery, Joachim; Stampfer, Meir J; Rudich, Assaf; Shai, Iris

    2016-08-01

    It remains unclear whether intermuscular adipose tissue (IMAT) has any metabolic influence or whether it is merely a marker of abnormalities, as well as what are the effects of specific lifestyle strategies for weight loss on the dynamics of both IMAT and thigh muscle area (TMA). We followed the trajectory of IMAT and TMA during 18-mo lifestyle intervention among 278 sedentary participants with abdominal obesity, using magnetic resonance imaging. We measured the resting metabolic rate (RMR) by an indirect calorimeter. Among 273 eligible participants (47.8 ± 9.3 yr of age), the mean IMAT was 9.6 ± 4.6 cm(2) Baseline IMAT levels were directly correlated with waist circumference, abdominal subdepots, C-reactive protein, and leptin and inversely correlated with baseline TMA and creatinine (P < 0.05 for all). After 18 mo (86.3% adherence), both IMAT (-1.6%) and TMA (-3.3%) significantly decreased (P < 0.01 vs. baseline). The changes in both IMAT and TMA were similar across the lifestyle intervention groups and directly corresponded with moderate weight loss (P < 0.001). IMAT change did not remain independently associated with decreased abdominal subdepots or improved cardiometabolic parameters after adjustments for age, sex, and 18-mo weight loss. In similar models, 18-mo TMA loss remained associated with decreased RMR, decreased activity, and with increased fasting glucose levels and IMAT (P < 0.05 for all). Unlike other fat depots, IMAT may not represent a unique or specific adipose tissue, instead largely reflecting body weight change per se. Moderate weight loss induced a significant decrease in thigh muscle area, suggesting the importance of resistance training to accompany weight loss programs. PMID:27402560

  14. Muscle sarcomere lesions and thrombosis after spaceflight and suspension unloading

    SciTech Connect

    Riley, D.A.; Ellis, S.; Giometti, C.S.; Hoh, J.F.Y.; Ilyina-Kakueva, E.I.; Oganov, V.S.; Slocum, G.R.; Bain, J.L.W.; Sedlak, F.R. )

    1992-08-01

    Extended exposure of humans to spaceflight produces a progressive loss of skeletal muscle strength. This process must be understood to design effective countermeasures. The present investigation examined hindlimb muscles from flight rats killed as close to landing as possible. Spaceflight and tail suspension-hindlimb unloading (unloaded) produced significant decreases in fiber cross-sectional areas of the adductor longus (AL), a slow-twitch antigravity muscle. However, the mean wet weight of the flight AL muscles was near normal, whereas that of the suspension unloaded AL muscles was significantly reduced. Interstitial edema within the flight AL, but not in the unloaded AL, appeared to account for this apparent disagreement.In both conditions, the slow-twitch oxidative fibers atrophied more than the fast-twitch oxidative-glycolytic fibers. Microcirculation was also compromised by spaceflight, such that there was increased formation of thrombi in the postcapillary venules and capillaries.

  15. Response of arterial resistance and critical pressure to changes in perfusion pressure in canine hindlimb.

    PubMed

    Shrier, I; Magder, S

    1993-12-01

    The dynamic pressure-flow relationship in the canine hindlimb at normal arterial pressure is best explained by modeling a Starling resistor (critical pressure, Pcrit) at the level of the arterioles. Regulation of flow can therefore occur at the Starling resistor through changes in Pcrit or along the length of the vessel through changes in arterial resistance (Ra). We hypothesized that increasing perfusion pressure (Pper) would increase Pcrit due to the myogenic response but would decrease Ra because of flow-mediated vasodilation and passive effects. We pump-perfused vascularly isolated hindlimbs of anesthetized dogs and then measured Pcrit and calculated Ra over Pper range of 75-175 mmHg. When Pper was increased from 75 to 175 mmHg, Pcrit increased from 33 +/- 2 to 48 +/- 6 (means +/- SE) mmHg, whereas Ra decreased from 10.1 +/- 1.2 to 7.86 +/- 0.7 mmHg.min.100 g.ml-1 (P < 0.01). Thus the responses of Pcrit and Ra to an increase in Pper were dissociated. In a second part of the study, we lowered carotid sinus pressure to determine the effects of central factors on local autoregulation. A decrease in carotid sinus pressure increased Pcrit and Ra at each Pper (P < 0.05). We conclude that an increase in Pper causes the arterial vasculature to constrict at the level of the Starling resistor and dilate more proximally. The carotid baroreflex causes an increase in tone throughout the arterial vasculature but does not alter the local response to increases in Pper. PMID:8285232

  16. Adaptation of the hindlimbs for climbing in bears.

    PubMed

    Sasaki, Motoki; Endo, Hideki; Wiig, Oystein; Derocher, Andrew E; Tsubota, Toshio; Taru, Hajime; Yamamoto, Masako; Arishima, Kazuyoshi; Hayashi, Yoshihiro; Kitamura, Nobuo; Yamada, Junzo

    2005-04-01

    The hindlimbs of the Malayan sun bear (Helarctos malayanus), the polar bear (Ursus maritimus), the brown bear (Ursus arctos) and the giant panda (Ailuropoda melanoleuca) have been anatomically and osteometrically studied. The Musculus tibialis cranialis of the Malayan sun bear and the giant panda possessed a well-developed rich fleshy portion until the distal end of the tibia. In the polar bear and the brown bear, however, the fleshy portion of the M. tibialis cranialis was not developed until the distal end of the tibia. The tendon of the M. tibialis cranialis inserting on the proximal end of the Ossa metatarsalia was shorter in the Malayan sun bear and the giant panda than in the polar bear and the brown bear. In the Malayan sun bear and the giant panda, moreover, the M. popliteus was attached more distally to the tibia than in the polar bear and the brown bear. The stable dorsiflexion and supination of the foot and the efficient pronation of the crus are important for skillful tree climbing. The present study suggests that the Malayan sun bear and the giant panda have hindlimbs especially adapted to tree climbing by the well-developed fleshy portion of the M. tibialis cranialis reaching the distal end of the tibia, its short tendon, and the M. popliteus inserting near the distal end of the tibia. PMID:15900701

  17. The combined effects of X-ray radiation and hindlimb suspension on bone loss.

    PubMed

    Xu, Dan; Zhao, Xin; Li, Yi; Ji, Yinli; Zhang, Jiangyan; Wang, Jufang; Xie, Xiaodong; Zhou, Guangming

    2014-07-01

    Outer space is a complex environment with various phenomena that negatively affect bone metabolism, including microgravity and highly energized ionizing radiation. In the present study, we used four groups of male Wistar rats treated with or without four-week hindlimb suspension after 4 Gy of X-rays to test whether there is a combined effect for hindlimb suspension and X-ray radiation. We tested trabecular parameters and some cytokines of the bone as leading indicators of bone metabolism. The results showed that hindlimb suspension and X-ray radiation could cause a significant increase in bone loss. Hindlimb suspension caused a 56.6% bone loss (P = 0.036), while X-ray radiation caused a 30.7% (P = 0.041) bone loss when compared with the control group. The combined factors of hindlimb suspension and X-rays exerted a combined effect on bone mass, with a reduction of 64.8% (P = 0.003).

  18. Hamiltonian Dynamics of a Forced Two-Degree-of-Freedom Arm with Viscoelastic Muscles Executing Planned Motions

    NASA Astrophysics Data System (ADS)

    Patra, Sayan; Ojakangas, Greg; Chase, Andrew; Chakrabarti, Anish; Sivils, Dalton; Johnson, Evan; Barrett, Kiefer; North, Mason; Julian, Preston

    2011-10-01

    In order to improve our understanding of how the brain controls the human arm both in the presence and absence of gravity, we have developed a two-degree-of-freedom robotic arm which is driven by six servo-actuated viscoelastic muscles. The computer-controlled servos mimic the contractive action of the sarcomeres in actual muscles, sections of elastic tubing represent the elastic behavior of actual muscles, while the behavior of tendons is represented by inelastic strings. The servos receive instructions to move from the visual C++ platform in the computer and the actual motion of the arm is recorded with optical encoders built into each joint axis. This experiment is a purely feed-forward system, and our goal is to determine whether our equations of motion, formulated using Hamiltonian dynamics, when numerically integrated, will predict the observed motion of the arm within experimental uncertainties.

  19. Hindlimb movement modulates the activity of rostral fastigial nucleus neurons that process vestibular input

    PubMed Central

    McCall, Andrew A; Miller, Daniel J; Catanzaro, Michael F; Cotter, Lucy A; Yates, Bill J

    2015-01-01

    Integration of vestibular and proprioceptive afferent information within the central nervous system is a critical component of postural regulation. We recently demonstrated that labyrinthine and hindlimb signals converge onto vestibular nucleus neurons, such that hindlimb movement modulates the activity of these cells. However, it is unclear whether similar convergence of hindlimb and vestibular signals also occurs upstream from the vestibular nuclei, particularly in the rostral fastigial nucleus (rFN). We tested the hypothesis that rFN neurons have similar responses to hindlimb movement as vestibular nucleus neurons. Recordings were obtained from 53 rFN neurons that responded to hindlimb movement in decerebrate cats. In contrast to vestibular nucleus neurons, which commonly encoded the direction of hindlimb movement (81% of neurons), few rFN neurons (21%) that responded to leg movement encoded such information. Instead, most rFN neurons responded to both limb flexion and extension. Half of the rFN neurons whose activity was modulated by hindlimb movement received convergent vestibular inputs. These results show that rFN neurons receive somatosensory inputs from the hindlimb, and that a subset of rFN neurons integrates vestibular and hindlimb signals. Such rFN neurons likely perform computations that participate in maintenance of balance during upright stance and movement. Although vestibular nucleus neurons are interconnected with the rFN, the dissimilarity of responses of neurons sensitive to hindlimb movement in the two regions suggest that they play different roles in coordinating postural responses during locomotion and other movements which entail changes in limb position. PMID:25976518

  20. Forelimb EMG-based trigger to control an electronic spinal bridge to enable hindlimb stepping after a complete spinal cord lesion in rats

    PubMed Central

    2012-01-01

    Background A complete spinal cord transection results in loss of all supraspinal motor control below the level of the injury. The neural circuitry in the lumbosacral spinal cord, however, can generate locomotor patterns in the hindlimbs of rats and cats with the aid of motor training, epidural stimulation and/or administration of monoaminergic agonists. We hypothesized that there are patterns of EMG signals from the forelimbs during quadrupedal locomotion that uniquely represent a signal for the “intent” to step with the hindlimbs. These observations led us to determine whether this type of “indirect” volitional control of stepping can be achieved after a complete spinal cord injury. The objective of this study was to develop an electronic bridge across the lesion of the spinal cord to facilitate hindlimb stepping after a complete mid-thoracic spinal cord injury in adult rats. Methods We developed an electronic spinal bridge that can detect specific patterns of EMG activity from the forelimb muscles to initiate electrical-enabling motor control (eEmc) of the lumbosacral spinal cord to enable quadrupedal stepping after a complete spinal cord transection in rats. A moving window detection algorithm was implemented in a small microprocessor to detect biceps brachii EMG activity bilaterally that then was used to initiate and terminate epidural stimulation in the lumbosacral spinal cord. We found dominant frequencies of 180–220 Hz in the EMG of the forelimb muscles during active periods, whereas these frequencies were between 0–10 Hz when the muscles were inactive. Results and conclusions Once the algorithm was validated to represent kinematically appropriate quadrupedal stepping, we observed that the algorithm could reliably detect, initiate, and facilitate stepping under different pharmacological conditions and at various treadmill speeds. PMID:22691460

  1. Insulin resistance for glucose metabolism in disused soleus muscle of mice

    NASA Technical Reports Server (NTRS)

    Seider, M. J.; Nicholson, W. F.; Booth, F. W.

    1981-01-01

    Results of this study on mice provide the first direct evidence of insulin resistance for glucose metabolism in skeletal muscle that has undergone a previous period of reduced muscle usage. This lack of responsiveness to insulin developed in one day and in the presence of hypoinsulinemia. Future studies will utilize the model of hindlimb immobilization to determine the causes of these changes.

  2. Four things to know about myosin light chains as reporters for non-muscle myosin-2 dynamics in live cells.

    PubMed

    Heissler, Sarah M; Sellers, James R

    2015-02-01

    The interplay between non-muscle myosins-2 and filamentous actin results in cytoplasmic contractility which is essential for eukaryotic life. Concomitantly, there is tremendous interest in elucidating the physiological function and temporal localization of non-muscle myosin-2 in cells. A commonly used method to study the function and localization of non-muscle myosin-2 is to overexpress a fluorescent protein (FP)-tagged version of the regulatory light chain (RLC) which binds to the myosin-2 heavy chain by mass action. Caveats about this approach include findings from recent studies indicating that the RLC does not bind exclusively to the non-muscle myosin-2 heavy chain. Rather, it can also associate with the myosin heavy chains of several other classes as well as other targets than myosin. In addition, the presence of the FP moiety may compromise myosin's enzymatic and mechanical performance. This and other factors to be discussed in this commentary raise questions about the possible complications in using FP-RLC as a marker for the dynamic localization and regulatory aspects of non-muscle myosin-2 motor functions in cell biological experiments.

  3. Influence of parallel spring-loaded exoskeleton on ankle muscle-tendon dynamics during simulated human hopping.

    PubMed

    Robertson, Benjamin D; Sawicki, Gregory S

    2011-01-01

    Robotic assistance for rehabilitation and enhancement of human locomotion has become a major goal of biomedical engineers in recent years. While significant progress to this end has been made in the fields of neural interfacing and control systems, little has been done to examine the effects of mechanical assistance on the biomechanics of underlying muscle-tendon systems. Here, we model the effects of mechanical assistance via a passive spring acting in parallel with the triceps surae-Achilles tendon complex during cyclic hopping in humans. We examine system dynamics over a range of biological muscle activation and exoskeleton spring stiffness. We find that, in most cases, uniform cyclic mechanical power production of the coupled system is achieved. Furthermore, unassisted power production can be reproduced throughout parameter space by trading off decreases in muscle activation with increases in ankle exoskeleton spring stiffness. In addition, we show that as mechanical assistance increases the biological muscle-tendon unit becomes less 'tuned' resulting in higher mechanical power output from active components of muscle despite large reductions in required force output.

  4. Tramadol Alleviates Myocardial Injury Induced by Acute Hindlimb Ischemia Reperfusion in Rats

    PubMed Central

    Takhtfooladi, Hamed Ashrafzadeh; Asl, Adel Haghighi Khiabanian; Shahzamani, Mehran; Takhtfooladi, Mohammad Ashrafzadeh; Allahverdi, Amin; Khansari, Mohammadreza

    2015-01-01

    Background Organ injury occurs not only during periods of ischemia but also during reperfusion. It is known that ischemia reperfusion (IR) causes both remote organ and local injuries. Objective This study evaluated the effects of tramadol on the heart as a remote organ after acute hindlimb IR. Methods Thirty healthy mature male Wistar rats were allocated randomly into three groups: Group I (sham), Group II (IR), and Group III (IR + tramadol). Ischemia was induced in anesthetized rats by left femoral artery clamping for 3 h, followed by 3 h of reperfusion. Tramadol (20 mg/kg, intravenous) was administered immediately prior to reperfusion. At the end of the reperfusion, animals were euthanized, and hearts were harvested for histological and biochemical examination. Results The levels of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were higher in Groups I and III than those in Group II (p < 0.05). In comparison with other groups, tissue malondialdehyde (MDA) levels in Group II were significantly increased (p < 0.05), and this increase was prevented by tramadol. Histopathological changes, including microscopic bleeding, edema, neutrophil infiltration, and necrosis, were scored. The total injuryscore in Group III was significantly decreased (p < 0.05) compared with Group II. Conclusion From the histological and biochemical perspectives, treatment with tramadol alleviated the myocardial injuries induced by skeletal muscle IR in this experimental model. PMID:26039663

  5. Measurement of osmotic reflection coefficient for small molecules in cat hindlimbs.

    PubMed

    Wolf, M B; Watson, P D

    1989-01-01

    Capillary osmotic reflection coefficients (sigma) for NaCl, urea, sucrose, and raffinose were measured in the isolated, perfused cat hindlimb using the osmotic transient technique. sigma were determined from the ratio of the maximum rate of transcapillary absorption [delta Jv(max)] to the increase in the osmotic pressure (25-35 mosmol/kg H2O) in the arterial inflow (delta pi a) produced by adding one of the molecules to an albumin-electrolyte perfusate containing isoproterenol (greater than 10(-7) M). delta Jv (max) was determined from organ weight and delta pi a from perfusate osmolalities. For each molecule, the delta Jv(max)/delta pi a ratio increased monotonically with perfusate flow rates (Q) to Q greater than 100 ml.min-1.100 g-1. This ratio was independent of the size of the delta pi a. Apparent sigma values were calculated by dividing these ratios by the capillary hydraulic capacity determined in other studies. At low Q, apparent sigma was comparable to the approximately 0.1 values found by others in skeletal muscle. At the highest Q, apparent sigma for these molecules were at least 0.5. These data are consistent with at least 50% of transcapillary water flow moving through a water-exclusive pathway.

  6. Attenuated muscle metaboreflex-induced pressor response during postexercise muscle ischemia in renovascular hypertension

    PubMed Central

    Spranger, Marty D.; Kaur, Jasdeep; Sala-Mercado, Javier A.; Machado, Tiago M.; Krishnan, Abhinav C.; Alvarez, Alberto

    2015-01-01

    During dynamic exercise, muscle metaboreflex activation (MMA; induced via partial hindlimb ischemia) markedly increases mean arterial pressure (MAP), and MAP is sustained when the ischemia is maintained following the cessation of exercise (postexercise muscle ischemia, PEMI). We previously reported that the sustained pressor response during PEMI in normal individuals is driven by a sustained increase in cardiac output (CO) with no peripheral vasoconstriction. However, we have recently shown that the rise in CO with MMA is significantly blunted in hypertension (HTN). The mechanisms sustaining the pressor response during PEMI in HTN are unknown. In six chronically instrumented canines, hemodynamic responses were observed during rest, mild exercise (3.2 km/h), MMA, and PEMI in the same animals before and after the induction of HTN [Goldblatt two kidney, one clip (2K1C)]. In controls, MAP, CO and HR increased with MMA (+52 ± 6 mmHg, +2.1 ± 0.3 l/min, and +37 ± 7 beats per minute). After induction of HTN, MAP at rest increased from 97 ± 3 to 130 ± 4 mmHg, and the metaboreflex responses were markedly attenuated (+32 ± 5 mmHg, +0.6 ± 0.2 l/min, and +11 ± 3 bpm). During PEMI in HTN, HR and CO were not sustained, and MAP fell to normal recovery levels. We conclude that the attenuated metaboreflex-induced HR, CO, and MAP responses are not sustained during PEMI in HTN. PMID:25632024

  7. Age-Related Changes in Dynamic Postural Control and Attentional Demands are Minimally Affected by Local Muscle Fatigue

    PubMed Central

    Remaud, Anthony; Thuong-Cong, Cécile; Bilodeau, Martin

    2016-01-01

    Normal aging results in alterations in the visual, vestibular and somtaosensory systems, which in turn modify the control of balance. Muscle fatigue may exacerbate these age-related changes in sensory and motor functions, and also increase the attentional demands associated with dynamic postural control. The purpose of this study was to investigate the effect of aging on dynamic postural control and posture-related attentional demands before and after a plantar flexor fatigue protocol. Participants (young adults: n = 15; healthy seniors: n = 13) performed a dynamic postural task along the antero-posterior (AP) and the medio-lateral (ML) axes, with and without the addition of a simple reaction time (RT) task. The dynamic postural task consisted in following a moving circle on a computer screen with the representation of the center of pressure (COP). This protocol was repeated before and after a fatigue task where ankle plantar flexor muscles were targeted. The mean COP-target distance and the mean COP velocity were calculated for each trial. Cross-correlation analyses between the COP and target displacements were also performed. RTs were recorded during dual-task trials. Results showed that while young adults adopted an anticipatory control mode to move their COP as close as possible to the target center, seniors adopted a reactive control mode, lagging behind the target center. This resulted in longer COP-target distance and higher COP velocity in the latter group. Concurrently, RT increased more in seniors when switching from static stance to dynamic postural conditions, suggesting potential alterations in the central nervous system (CNS) functions. Finally, plantar flexor muscle fatigue and dual-tasking had only minor effects on dynamic postural control of both young adults and seniors. Future studies should investigate why the fatigue-induced changes in quiet standing postural control do not seem to transfer to dynamic balance tasks. PMID:26834626

  8. Changes in muscles accompanying non-weight-bearing and weightlessness

    NASA Technical Reports Server (NTRS)

    Tischler, M. E.; Henriksen, E. J.; Jaspers, S. R.; Jacob, S.; Kirby, C.

    1989-01-01

    Results of hindlimb suspension and space flight experiments with rats examine the effects of weightlessness simulation, weightlessness, and delay in postflight recovery of animals. Parameters examined were body mass, protein balance, amino acid metabolism, glucose and glycogen metabolism, and hormone levels. Tables show metabolic responses to unweighting of the soleus muscle.

  9. Comparison of four specific dynamic office chairs with a conventional office chair: impact upon muscle activation, physical activity and posture.

    PubMed

    Ellegast, Rolf P; Kraft, Kathrin; Groenesteijn, Liesbeth; Krause, Frank; Berger, Helmut; Vink, Peter

    2012-03-01

    Prolonged and static sitting postures provoke physical inactivity at VDU workplaces and are therefore discussed as risk factors for the musculoskeletal system. Manufacturers have designed specific dynamic office chairs featuring structural elements which promote dynamic sitting and therefore physical activity. The aim of the present study was to evaluate the effects of four specific dynamic chairs on erector spinae and trapezius EMG, postures/joint angles and physical activity intensity (PAI) compared to those of a conventional standard office chair. All chairs were fitted with sensors for measurement of the chair parameters (backrest inclination, forward and sideward seat pan inclination), and tested in the laboratory by 10 subjects performing 7 standardized office tasks and by another 12 subjects in the field during their normal office work. Muscle activation revealed no significant differences between the specific dynamic chairs and the reference chair. Analysis of postures/joint angles and PAI revealed only a few differences between the chairs, whereas the tasks performed strongly affected the measured muscle activation, postures and kinematics. The characteristic dynamic elements of each specific chair yielded significant differences in the measured chair parameters, but these characteristics did not appear to affect the sitting dynamics of the subjects performing their office tasks.

  10. Assessment of hindlimb locomotor strength in spinal cord transected rats through animal-robot contact force.

    PubMed

    Nessler, Jeff A; Moustafa-Bayoumi, Moustafa; Soto, Dalziel; Duhon, Jessica; Schmitt, Ryan

    2011-12-01

    measurement of animal-robot contact forces using the instrumented rat stepper can provide a sensitive and reliable measure of hindlimb locomotor strength and control of flexor and extensor muscle activity in neurologically impaired animals. Additionally, these measures may be useful as a means to quantify training intensity or dose-related functional outcomes of automated training.

  11. Thunniform swimming: muscle dynamics and mechanical power production of aerobic fibres in yellowfin tuna (Thunnus albacares).

    PubMed

    Shadwick, Robert E; Syme, Douglas A

    2008-05-01

    We studied the mechanical properties of deep red aerobic muscle of yellowfin tuna (Thunnus albacares), using both in vivo and in vitro methods. In fish swimming in a water tunnel at 1-3 L s(-1) (where L is fork length), muscle length changes were recorded by sonomicrometry, and activation timing was quantified by electromyography. In some fish a tendon buckle was also implanted on the caudal tendon to measure instantaneous muscle forces transmitted to the tail. Between measurement sites at 0.45 to 0.65 L, the wave of muscle shortening progressed along the body at a relatively high velocity of 1.7 L per tail beat period, and a significant phase shift (31+/-4 degrees ) occurred between muscle shortening and local midline curvature, both suggesting red muscle power is directed posteriorly, rather than causing local body bending, which is a hallmark of thunniform swimming. Muscle activation at 0.53 L was initiated at about 50 degrees of the tail beat period and ceased at about 160 degrees , where 90 degrees is peak muscle length and 180 degrees is minimum length. Strain amplitude in the deep red fibres at 0.5 L was +/-5.4%, double that predicted from midline curvature analysis. Work and power production were measured in isolated bundles of red fibres from 0.5 L by the work loop technique. Power was maximal at 3-4 Hz and fell to less than 50% of maximum after 6 Hz. Based on the timing of activation, muscle strain, tail beat frequencies and forces in the caudal tendon while swimming, we conclude that yellowfin tuna, like skipjack, use their red muscles under conditions that produce near-maximal power output while swimming. Interestingly, the red muscles of yellowfin tuna are slower than those of skipjack, which corresponds with the slower tail beat frequencies and cruising speeds in yellowfin. PMID:18456888

  12. Caveolae regulate vasoconstriction of conduit arteries to angiotensin II in hindlimb unweighted rats.

    PubMed

    Wang, Zhongchao; Bai, Yungang; Yu, Jinwen; Liu, Huan; Cheng, Yaoping; Liu, Yonghong; Xie, Xiaoping; Ma, Jin; Bao, Junxiang

    2015-10-15

    Weightlessness induces the functional remodelling of arteries, but the changes to angiotensin II (Ang II)-elicited vasoconstriction and the underlying mechanism have never been reported. Caveolae are invaginations of the cell membrane crucial for the contraction of vascular smooth muscle cells, so we investigated the adaptation of Ang II-elicited vasoconstriction to simulated weightlessness and the role of caveolae in it. The 4 week hindlimb unweighted (HU) rat was used to simulate the effects of weightlessness. Ang II-elicited vasoconstriction was measured by isometric force recording. The morphology of caveolae was examined by transmission electron microscope. The binding of the angiotensin II type 1 receptor (AT1 ) and caveolin-1 (cav-1) was examined by coimmunoprecipitation and Western blot. We found that the maximal developing force (E(max)) of Ang II-elicited vasoconstriction was decreased in abdominal aorta by 30.6%, unchanged in thoracic aorta and increased in carotid artery by 17.9% after HU, while EC50 of the response was increased in all three arteries (P < 0.05). AT1 desensitization upon activation was significantly reduced by HU in all three arteries, as was the number of caveolae (P < 0.05). Furthermore, Ang II promoted the binding of AT1 and cav-1 significantly in control but not HU arteries. Both the number of caveolae and the binding of AT1 and cav-1 in HU arteries were restored by cholesterol pretreatment which also reinstated the change in EC50 as well as the level of AT1 desensitization. These results indicate that modified caveolae in vascular smooth muscle cells could interfere with the binding of AT1 and cav-1 mediating the adaptation of Ang II-elicited vasoconstriction to HU.

  13. The Effects of Diuretics on Intracellular Ca2+ Dynamics of Arteriole Smooth Muscles as Revealed by Laser Confocal Microscopy

    PubMed Central

    Tamagawa, Yasunori; Saino, Tomoyuki; Matsuura, Makoto; Satoh, Yoh-ichi

    2009-01-01

    The regulation of cytosolic Ca2+ homeostasis is essential for cells, including vascular smooth muscle cells. Arterial tone, which underlies the maintenance of peripheral resistance in the circulation, is a major contributor to the control of blood pressure. Diuretics may regulate intracellular Ca2+ concentration ([Ca2+]i) and have an effect on vascular tone. In order to investigate the influence of diuretics on peripheral resistance in circulation, we investigated the alteration of [Ca2+]i in testicular arterioles with respect to several categories of diuretics using real-time confocal laser scanning microscopy. In this study, hydrochlorothiazide (100 µM) and furosemide (100 µM) had no effect on the [Ca2+]i dynamics. However, when spironolactone (300 µM) was applied, the [Ca2+]i of smooth muscles increased. The response was considerably inhibited under either extracellular Ca2+-free conditions, the presence of Gd3+, or with a treatment of diltiazem. After the thapsigargin-induced depletion of internal Ca2+ store, the spironolactone-induced [Ca2+]i dynamics was slightly inhibited. Therefore, the spironolactone-induced dynamics of [Ca2+]i can be caused by either a Ca2+ influx from extracellular fluid or Ca2+ mobilization from internal Ca2+ store, with the former being dominant. As tetraethylammonium, an inhibitor of the K+ channel, slightly inhibited the spironolactone-induced [Ca2+]i dynamics, the K+ channel might play a minor role in those dynamics. Tetrodotoxin, a neurotoxic Na+ channel blocker, had no effect, therefore the spironolactone-induced dynamics is a direct effect to smooth muscles, rather than an indirect effect via vessel nerves. PMID:19759873

  14. VCP-dependent muscle degeneration is linked to defects in a dynamic tubular lysosomal network in vivo

    PubMed Central

    Johnson, Alyssa E; Shu, Huidy; Hauswirth, Anna G; Tong, Amy; Davis, Graeme W

    2015-01-01

    Lysosomes are classically viewed as vesicular structures to which cargos are delivered for degradation. Here, we identify a network of dynamic, tubular lysosomes that extends throughout Drosophila muscle, in vivo. Live imaging reveals that autophagosomes merge with tubular lysosomes and that lysosomal membranes undergo extension, retraction, fusion and fission. The dynamics and integrity of this tubular lysosomal network requires VCP, an AAA-ATPase that, when mutated, causes degenerative diseases of muscle, bone and neurons. We show that human VCP rescues the defects caused by loss of Drosophila VCP and overexpression of disease relevant VCP transgenes dismantles tubular lysosomes, linking tubular lysosome dysfunction to human VCP-related diseases. Finally, disruption of tubular lysosomes correlates with impaired autophagosome-lysosome fusion, increased cytoplasmic poly-ubiquitin aggregates, lipofuscin material, damaged mitochondria and impaired muscle function. We propose that VCP sustains sarcoplasmic proteostasis, in part, by controlling the integrity of a dynamic tubular lysosomal network. DOI: http://dx.doi.org/10.7554/eLife.07366.001 PMID:26167652

  15. Control of skeletal muscle perfusion at the onset of dynamic exercise

    NASA Technical Reports Server (NTRS)

    Delp, M. D.

    1999-01-01

    At the onset of exercise there is a rapid increase in skeletal muscle vascular conductance and blood flow. Several mechanisms involved in the regulation of muscle perfusion have been proposed to initiate this hyperemic response, including neural, metabolic, endothelial, myogenic, and muscle pump mechanisms. Investigators utilizing pharmacological blockade of cholinergic muscarinic receptors and sympathectomy have concluded that neither sympathetic cholinergic nor adrenergic neural mechanisms are involved in the initial hyperemia. Studies have also shown that the time course for vasoactive metabolite release, diffusion, accumulation, and action is too long to account for the rapid increase in vascular conductance at the initiation of exercise. Furthermore, there is little or no evidence to support an endothelium or myogenic mechanism as the initiating factor in the muscle hyperemia. Thus, the rise in muscle blood flow does not appear to be explained by known neural, metabolic, endothelial, or myogenic influences. However, the initial hyperemia is consistent with the mechanical effects of the muscle pump to increase the arteriovenous pressure gradient across muscle. Because skeletal muscle blood flow is regulated by multiple and redundant mechanisms, it is likely that neural, metabolic, and possibly endothelial factors become important modulators of mechanically induced exercise hyperemia following the first 5-10 s of exercise.

  16. Wave reflection and central aortic pressure are increased in response to static and dynamic muscle contraction at comparable workloads.

    PubMed

    Edwards, David G; Mastin, Corey R; Kenefick, Robert W

    2008-02-01

    We determined the effects of static and dynamic muscle contraction at equivalent workloads on central aortic pressure and wave reflection. At random, 14 healthy men and women (23 +/- 5 yr of age) performed a static handgrip forearm contraction [90 s at 30% of maximal voluntary contraction (MVC)], dynamic handgrip contractions (1 contraction/s for 180 s at 30% MVC), and a control trial. During static and dynamic trials, tension-time index was controlled by holding peak tension constant. Measurements of brachial artery blood pressure and the synthesis of a central aortic pressure waveform (by radial artery applanation tonometry and generalized transfer function) were conducted at baseline, during each trial, and during 1 min of postexercise ischemia (PEI). Aortic augmentation index (AI), an index of wave reflection, was calculated from the aortic pressure waveform. AI increased during both static and dynamic trials (static, 5.2 +/- 3.1 to 11.8 +/- 3.4%; dynamic, 5.8 +/- 3.0 to 13.3 +/- 3.4%; P < 0.05) and further increased during PEI (static, 18.5 +/- 3.1%; dynamic, 18.6 +/- 2.9%; P < 0.05). Peripheral and central systolic and diastolic pressures increased (P < 0.05) during both static and dynamic trials and remained elevated during PEI. AI and pressure responses did not differ between static and dynamic trials. Peripheral and central pressures increased similarly during static and dynamic contraction; however, the rise in central systolic pressure during both conditions was augmented by increased wave reflection. The present data suggest that wave reflection is an important determinant of the central blood pressure response during forearm muscle contractions.

  17. Gene Regions Responding to Skeletal Muscle Atrophy

    NASA Technical Reports Server (NTRS)

    Booth, Frank W.

    1997-01-01

    Our stated specific aims for this project were: 1) Identify the region(s) of the mouse IIb myosin heavy chain (MHC) promoter necessary for in vivo expression in mouse fast-twitch muscle, and 2) Identify the region(s) of the mouse IIb MHC promoter responsive to immobilization in mouse slow-twitch muscle in vivo. We sought to address these specific aims by introducing various MHC IIb promoter/reporter gene constructs directly into the tibialis anterior and gastrocnemius muscles of living mice. Although the method of somatic gene transfer into skeletal muscle by direct injection has been successfully used in our laboratory to study the regulation of the skeletal alpha actin gene in chicken skeletal muscle, we had many difficulties utilizing this procedure in the mouse. Because of the small size of the mouse soleus and the difficulty in obtaining consistent results, we elected not to study this muscle as first proposed. Rather, our MHC IIb promoter deletion experiments were performed in the gastrocnemius. Further, we decided to use hindlimb unloading via tail suspension to induce an upregulation of the MHC IIb gene, rather than immobilization of the hindlimbs via plaster casts. This change was made because tail suspension more closely mimics spaceflight, and this procedure in our lab results in a smaller loss of overall body mass than the mouse hindlimb immobilization procedure. This suggests that the stress level during tail suspension is less than during immobilization. This research has provided an important beginning point towards understanding the molecular regulation of the MHC lIb gene in response to unweighting of skeletal muscle Future work will focus on the regulation of MHC IIb mRNA stability in response to altered loading of skeletal muscle

  18. FMAj: a tool for high content analysis of muscle dynamics in Drosophila metamorphosis

    PubMed Central

    2014-01-01

    Background During metamorphosis in Drosophila melanogaster, larval muscles undergo two different developmental fates; one population is removed by cell death, while the other persistent subset undergoes morphological remodeling and survives to adulthood. Thanks to the ability to perform live imaging of muscle development in transparent pupae and the power of genetics, metamorphosis in Drosophila can be used as a model to study the regulation of skeletal muscle mass. However, time-lapse microscopy generates sizeable image data that require new tools for high throughput image analysis. Results We performed targeted gene perturbation in muscles and acquired 3D time-series images of muscles in metamorphosis using laser scanning confocal microscopy. To quantify the phenotypic effects of gene perturbations, we designed the Fly Muscle Analysis tool (FMAj) which is based on the ImageJ and MySQL frameworks for image processing and data storage, respectively. The image analysis pipeline of FMAj contains three modules. The first module assists in adding annotations to time-lapse datasets, such as genotypes, experimental parameters and temporal reference points, which are used to compare different datasets. The second module performs segmentation and feature extraction of muscle cells and nuclei. Users can provide annotations to the detected objects, such as muscle identities and anatomical information. The third module performs comparative quantitative analysis of muscle phenotypes. We applied our tool to the phenotypic characterization of two atrophy related genes that were silenced by RNA interference. Reduction of Drosophila Tor (Target of Rapamycin) expression resulted in enhanced atrophy compared to control, while inhibition of the autophagy factor Atg9 caused suppression of atrophy and enlarged muscle fibers of abnormal morphology. FMAj enabled us to monitor the progression of atrophic and hypertrophic phenotypes of individual muscles throughout metamorphosis

  19. The influence of muscles activation on the dynamical behaviour of the tympano-ossicular system of the middle ear.

    PubMed

    Gentil, Fernanda; Parente, Marco; Martins, Pedro; Garbe, Carolina; Paço, João; Ferreira, António J M; Tavares, João Manuel R S; Jorge, Renato Natal

    2013-04-01

    The human ear is a complex biomechanical system and is divided into three parts: outer, middle and inner ear. The middle ear is formed by ossicles (malleus, incus and stapes), ligaments, muscles and tendons, which transfers sound vibrations from the eardrum to the inner ear, linking with mastoid and Eustachian tube. In this work, a finite element modelling of the tympano-ossicular system of the middle ear was developed. A dynamic study based on a structural response to harmonic vibrations, for a sound pressure level (SPL) of 110, 120 and 130 dB SPL applied in the eardrum, is presented. The connection between the ossicles is made using a contact formulation. The model includes the different ligaments considering its hyperelastic behaviour. The activation of the muscles is based on the constitutive model proposed by previous work. The harmonic responses of displacement and pressure obtained on the stapes footplate, for a frequency range between 100 Hz and 10 kHz, are obtained simulating the muscle activation. The results are compared considering the passive and active states. The results are discussed and they are in accordance with audiological data published with reference to the effects of the middle ear muscles contraction.

  20. Functional muscle synergies constrain force production during postural tasks

    PubMed Central

    McKay, J. Lucas; Ting, Lena H.

    2015-01-01

    We recently demonstrated that a set of five functional muscle synergies were sufficient to characterize both hindlimb muscle activity and active forces during automatic postural responses in cats standing at multiple postural configurations. This characterization depended critically upon the assumption that the endpoint force vector (synergy force vector) produced by the activation of each muscle synergy rotated with the limb axis as the hindlimb posture varied in the sagittal plane. Here, we used a detailed, 3D static model of the hindlimb to confirm that this assumption is biomechanically plausible: as we varied the model posture, simulated synergy force vectors rotated monotonically with the limb axis in the parasagittal plane (r2 = 0.94 ± 0.08). We then tested whether a neural strategy of using these five functional muscle synergies provides the same force-generating capability as controlling each of the 31 muscles individually. We compared feasible force sets (FFS) from the model with and without a muscle synergy organization. FFS volumes were significantly reduced with the muscle synergy organization (F = 1556.01, p ≪ 0.01), and as posture varied, the synergy-limited FFSs changed in shape, consistent with changes in experimentally-measured active forces. In contrast, nominal FFS shapes were invariant with posture, reinforcing prior findings that postural forces cannot be predicted by hindlimb biomechanics alone. We propose that an internal model for postural force generation may coordinate functional muscle synergies that are invariant in intrinsic limb coordinates, and this reduced-dimension control scheme reduces the set of forces available for postural control. PMID:17980370

  1. Fusimotor control of muscle spindle sensitivity during respiration in the cat.

    PubMed Central

    Greer, J J; Stein, R B

    1990-01-01

    1. The two types of fusimotor neurones, dynamic and static, can be differentiated by their effects on muscle spindle afferents. We have recorded the activity of muscle spindle primary afferents from the intercostal nerves of anaesthetized or decerebrate cats. A 4 Hz sinusoidal stretch was applied to the muscle containing the spindles of interest before and after crushing the nerve proximal to the recording site to eliminate fusimotor effects. The relative activity of the dynamic and static fusimotor neurones was inferred from the change in the spindle afferents' response. 2. Some areas of intercostal muscle normally showed phasic activity linked to respiration, where as other areas of intercostal muscle showed no EMG activity under our experimental conditions. In areas of intercostal muscle lacking EMG activity, the afferents' mean rate was higher and the modulation around the mean was lower at all phases of the breathing cycle when the efferent supply was intact. This result suggests the muscle spindles were receiving a steady level of static fusimotor activity. 3. Spindle primary afferents from regions of intercostal muscle that were typically recruited during respiration had an additional increase in mean rate and modulation around the mean rate in phase with the EMG activity. This is suggestive of phasic activation of dynamic fusimotor neurones in addition to static fusimotor discharge. 4. Thus, the two types of fusimotor neurones can be activated separately by the CNS to control the sensitivity of muscle spindles. The regional differences in the recruitment patterns of fusimotor neurones parallels the functional specializations of different areas of the intercostal muscles. The temporal modifications of fusimotor activity during each respiratory cycle means that the segmental reflex gain will vary in those intercostal muscles that are active during respiration. 5. These findings regarding the CNS recruitment of the two types of fusimotor neurones during

  2. Application of dynamic metabolomics to examine in vivo skeletal muscle glucose metabolism in the chronically high-fat fed mouse

    SciTech Connect

    Kowalski, Greg M.; De Souza, David P.; Burch, Micah L.; Hamley, Steven; Kloehn, Joachim; Selathurai, Ahrathy; Tull, Dedreia; O'Callaghan, Sean; McConville, Malcolm J.; Bruce, Clinton R.

    2015-06-19

    Rationale: Defects in muscle glucose metabolism are linked to type 2 diabetes. Mechanistic studies examining these defects rely on the use of high fat-fed rodent models and typically involve the determination of muscle glucose uptake under insulin-stimulated conditions. While insightful, they do not necessarily reflect the physiology of the postprandial state. In addition, most studies do not examine aspects of glucose metabolism beyond the uptake process. Here we present an approach to study rodent muscle glucose and intermediary metabolism under the dynamic and physiologically relevant setting of the oral glucose tolerance test (OGTT). Methods and results: In vivo muscle glucose and intermediary metabolism was investigated following oral administration of [U-{sup 13}C] glucose. Quadriceps muscles were collected 15 and 60 min after glucose administration and metabolite flux profiling was determined by measuring {sup 13}C mass isotopomers in glycolytic and tricarboxylic acid (TCA) cycle intermediates via gas chromatography–mass spectrometry. While no dietary effects were noted in the glycolytic pathway, muscle from mice fed a high fat diet (HFD) exhibited a reduction in labelling in TCA intermediates. Interestingly, this appeared to be independent of alterations in flux through pyruvate dehydrogenase. In addition, our findings suggest that TCA cycle anaplerosis is negligible in muscle during an OGTT. Conclusions: Under the dynamic physiologically relevant conditions of the OGTT, skeletal muscle from HFD fed mice exhibits alterations in glucose metabolism at the level of the TCA cycle. - Highlights: • Dynamic metabolomics was used to investigate muscle glucose metabolism in vivo. • Mitochondrial TCA cycle metabolism is altered in muscle of HFD mice. • This defect was not pyruvate dehydrogenase mediated, as has been previously thought. • Mitochondrial TCA cycle anaplerosis in muscle is virtually absent during the OGTT.

  3. The application of Hilbert-Huang transform in the analysis of muscle fatigue during cyclic dynamic contractions.

    PubMed

    Srhoj-Egekher, Vedran; Cifrek, Mario; Medved, Vladimir

    2011-06-01

    Surface electromyography (sEMG) is a common technique used in the assessment of local muscle fatigue. As opposed to static contraction situations, sEMG recordings during dynamic contractions are particularly characterised by non-stationary (and non-linear) features. Standard signal processing methods using Fourier and wavelet based procedures demonstrate well known restrictions on time-frequency resolution and the ability to process non-stationary and/or non-linear time-series, thus aggravating the spectral parameters estimation. The Hilbert-Huang transform (HHT), comprising of the empirical mode decomposition (EMD) and Hilbert spectral analysis (HSA), provides a new approach to overcome these issues. The time-dependent median frequency estimate is used as muscle fatigue indicator, and linear regression parameters are derived as fatigue quantifiers. The HHT method is utilised for the analysis of the sEMG signals recorded over quadriceps muscles during cyclic dynamic contractions. The results are compared with those obtained by the Fourier and wavelet based methods. It is shown that HHT procedure provides the most consistent and reliable assessment of spectral and derived linear regression parameters, given the time epoch width and sampling interval in the time domain. The suggested procedure successfully deals with non-stationary and non-linear properties of biomedical signals.

  4. [Relationship between simulated weightlessness-induced muscle spindle change and muscle atrophy].

    PubMed

    Zhao, Xue-Hong; Fan, Xiao-Li

    2013-02-25

    One of the most important and urgent issues in the field of space medicine is to reveal the potential mechanism underlying the disused muscle atrophy during the weightlessness or microgravity environment. It will conduce to find out effective methods for the prevention and treatment of muscle atrophy during a long-term space flight. Increasing data show that muscle spindle discharges are significantly altered following the hindlimb unloading, suggesting a vital role in the progress of muscle atrophy. In the last decades, we have made a series of studies on changes in the morphological structure and function of muscle spindle following simulated weightlessness. This review will discuss our main results and related researches for understanding of muscle spindle activities during microgravity environment, which may provide a theoretic basis for effective prevention and treatment of muscle atrophy induced by weightlessness. PMID:23426520

  5. Dynamic control of muscle stiffness and H reflex modulation during hopping and jumping in man.

    PubMed Central

    Dyhre-Poulsen, P; Simonsen, E B; Voigt, M

    1991-01-01

    1. The objective of the study was to evaluate the functional effects of reflexes on muscle mechanics during natural voluntary movements. The excitability of the H (Hoffmann) reflex was used as a measure of the excitability of the central component of the stretch reflex. 2. We recorded EMG, ground reaction forces and the H reflex in the soleus muscle in humans while landing from a downward jump, during drop jumping and during hopping. The movements were also recorded by high-speed cinematography. 3. The EMG pattern was adapted to the motor task. When landing the EMG in the soleus muscle and in the anterior tibial muscle showed preinnervation and alternating activity after touch down. When hopping there was little preinnervation in the soleus muscle, and the activity was initiated about 45 ms after touch down by a peak and continued unbroken until lift off. In the drop jumps the EMG pattern depended on the jumping style used by the subject. 4. The H reflex in the soleus muscle was strongly modulated in a manner appropriate to the requirements of the motor task. During landing from a downward jump the H reflex was low at touch down whereas while hopping it was high at touch down. During drop jumping it was variable and influenced by the jumping technique. 5. Muscle stiffness in the ankle joint was negative after touch down when landing, but always positive when hopping. 6. It is suggested that during landing the alternating EMG pattern after touch down was programmed and little influenced by reflexes. During hopping reflexes could contribute to the initial peak and the EMG during lift off. 7. The programmed EMG activity and the suppression of the H reflex while landing probably contribute to the development of the negative stiffness and change the muscles from a spring to a damping unit. PMID:1890636

  6. Fluoromicrometry: A Method for Measuring Muscle Length Dynamics with Biplanar Videofluoroscopy.

    PubMed

    Camp, Ariel L; Astley, Henry C; Horner, Angela M; Roberts, Thomas J; Brainerd, Elizabeth L

    2016-08-01

    Accurate measurements of muscle length changes are essential for understanding the biomechanics of musculoskeletal systems, and can provide insights into muscular work, force, and power. Muscle length has typically been measured in vivo using sonomicrometry, a method that measures distances by sending and receiving sound pulses between piezoelectric crystals. Here, we evaluate an alternative method, fluoromicrometry, which measures muscle length changes over time by tracking the three-dimensional positions of implanted, radio-opaque markers via biplanar videofluoroscopy. To determine the accuracy and precision of fluoromicrometry, we simultaneously measured length changes of an isolated muscle, the frog sartorius, in an in vitro setup using both fluoromicrometry and a servomotor. For fluoromicrometry to perfectly match the results of the servomotor, the relationship between the two measurements should be linear, with a slope of 1. Measurements of muscle shortening from fluoromicrometry and the motor were compared across 11 isotonic contractions. The precision of fluoromicrometry was ±0.09 mm, measured as the root mean square error of the regression of fluoromicrometry versus servomotor muscle lengths. Fluoromicrometry was also accurate: the mean slope of the fluoromicrometry-servomotor regressions did not differ significantly from the ideal line once off-axis motion was removed. Thus, fluoromicrometry provides a useful alternative for measuring muscle length, especially in studies of live animals, as it permits long-term marker implantation, wireless data collection, and increased spatial sampling. Fluoromicrometry can also be used with X-Ray Reconstruction of Moving Morphology to simultaneously measure muscle shortening and skeletal kinematics, providing a potent new tool for biomechanics research. PMID:27488475

  7. High-energy proton irradiation of C57Bl6 mice under hindlimb unloading

    NASA Astrophysics Data System (ADS)

    Mendonca, Marc; Todd, Paul; Orschell, Christie; Chin-Sinex, Helen; Farr, Jonathan; Klein, Susan; Sokol, Paul

    2012-07-01

    Solar proton events (SPEs) pose substantial risk for crewmembers on deep space missions. It has been shown that low gravity and ionizing radiation both produce transient anemia and immunodeficiencies. We utilized the C57Bl/6 based hindlimb suspension model to investigate the consequences of hindlimb-unloading induced immune suppression on the sensitivity to whole body irradiation with modulated 208 MeV protons. Eight-week old C57Bl/6 female mice were conditioned by hindlimb-unloading. Serial CBC and hematocrit assays by HEMAVET were accumulated for the hindlimb-unloaded mice and parallel control animals subjected to identical conditions without unloading. One week of hindlimb-unloading resulted in a persistent, statistically significant 10% reduction in RBC count and a persistent, statistically significant 35% drop in lymphocyte count. This inhibition is consistent with published observations of low Earth orbit flown mice and with crewmember blood analyses. In our experiments the cell count suppression was sustained for the entire six-week period of observation and persisted for at least 7 days beyond the period of active hindlimb-unloading. C57Bl/6 mice were also irradiated with 208 MeV Spread Out Bragg Peak (SOBP) protons at the Midwest Proton Radiotherapy Institute at the Indiana University Cyclotron Facility. We found that at 8.5 Gy hindlimb-unloaded mice were significantly more radiation sensitive with 35 lethalities out of 51 mice versus 15 out of 45 control (non-suspended) mice within 30 days of receiving 8.5 Gy of SOBP protons (p =0.001). Both control and hindlimb-unloaded stocktickerCBC analyses of 8.5 Gy proton irradiated and control mice by HEMAVET demonstrated severe reductions in WBC counts (Lymphocytes and PMNs) by day 2 post-irradiation, followed a week to ten days later by reductions in platelets, and then reductions in RBCs about 2 weeks post-irradiation. Recovery of all blood components commenced by three weeks post-irradiation. CBC analyses of 8

  8. Local GABA receptor blockade reveals hindlimb responses in the SI forelimb-stump representation of neonatally amputated rats.

    PubMed

    Pluto, Charles P; Lane, Richard D; Rhoades, Robert W

    2004-07-01

    In adult rats that sustained forelimb amputation on the day of birth, there are numerous multi-unit recording sites in the forelimb-stump representation of primary somatosensory cortex (SI) that also respond to cutaneous stimulation of the hindlimb when cortical receptors for GABA are blocked. These normally suppressed hindlimb inputs originate in the SI hindlimb representation and synapse in the dysgranular cortex before exciting SI forelimb-stump neurons. In our previous studies, GABA (A + B) receptor blockade was achieved by topically applying a bicuculline methiodide/saclofen solution (BMI/SAC) to the cortical surface. This treatment blocks receptors throughout SI and does not allow determination of where along the above circuit the GABA-mediated suppression of hindlimb information occurs. In this study, focal injections of BMI/SAC were delivered to three distinct cortical regions that are involved in the hindlimb-to-forelimb-stump pathway. Blocking GABA receptors in the SI hindlimb representation and in the dysgranular cortex was largely ineffective in revealing hindlimb inputs ( approximately 10% of hindlimb inputs were revealed in both cases). In contrast, when the blockade was targeted at forelimb-stump recording sites, >80% of hindlimb inputs were revealed. Thus GABAergic interneurons within the forelimb-stump representation suppress the expression of reorganized hindlimb inputs to the region. A circuit model incorporating these and previous observations is presented and discussed.

  9. Cellular dynamics of regeneration reveals role of two distinct Pax7 stem cell populations in larval zebrafish muscle repair

    PubMed Central

    Pipalia, Tapan G.; Koth, Jana; Roy, Shukolpa D.; Hammond, Christina L.; Kawakami, Koichi

    2016-01-01

    ABSTRACT Heterogeneity of stem cells or their niches is likely to influence tissue regeneration. Here we reveal stem/precursor cell diversity during wound repair in larval zebrafish somitic body muscle using time-lapse 3D confocal microscopy on reporter lines. Skeletal muscle with incision wounds rapidly regenerates both slow and fast muscle fibre types. A swift immune response is followed by an increase in cells at the wound site, many of which express the muscle stem cell marker Pax7. Pax7+ cells proliferate and then undergo terminal differentiation involving Myogenin accumulation and subsequent loss of Pax7 followed by elongation and fusion to repair fast muscle fibres. Analysis of pax7a and pax7b transgenic reporter fish reveals that cells expressing each of the duplicated pax7 genes are distinctly localised in uninjured larvae. Cells marked by pax7a only or by both pax7a and pax7b enter the wound rapidly and contribute to muscle wound repair, but each behaves differently. Low numbers of pax7a-only cells form nascent fibres. Time-lapse microscopy revealed that the more numerous pax7b-marked cells frequently fuse to pre-existing fibres, contributing more strongly than pax7a-only cells to repair of damaged fibres. pax7b-marked cells are more often present in rows of aligned cells that are observed to fuse into a single fibre, but more rarely contribute to nascent regenerated fibres. Ablation of a substantial portion of nitroreductase-expressing pax7b cells with metronidazole prior to wounding triggered rapid pax7a-only cell accumulation, but this neither inhibited nor augmented pax7a-only cell-derived myogenesis and thus altered the cellular repair dynamics during wound healing. Moreover, pax7a-only cells did not regenerate pax7b cells, suggesting a lineage distinction. We propose a modified founder cell and fusion-competent cell model in which pax7a-only cells initiate fibre formation and pax7b cells contribute to fibre growth. This newly discovered cellular

  10. Triclosan impairs excitation-contraction coupling and Ca2+ dynamics in striated muscle.

    PubMed

    Cherednichenko, Gennady; Zhang, Rui; Bannister, Roger A; Timofeyev, Valeriy; Li, Ning; Fritsch, Erika B; Feng, Wei; Barrientos, Genaro C; Schebb, Nils H; Hammock, Bruce D; Beam, Kurt G; Chiamvimonvat, Nipavan; Pessah, Isaac N

    2012-08-28

    Triclosan (TCS), a high-production-volume chemical used as a bactericide in personal care products, is a priority pollutant of growing concern to human and environmental health. TCS is capable of altering the activity of type 1 ryanodine receptor (RyR1), but its potential to influence physiological excitation-contraction coupling (ECC) and muscle function has not been investigated. Here, we report that TCS impairs ECC of both cardiac and skeletal muscle in vitro and in vivo. TCS acutely depresses hemodynamics and grip strength in mice at doses ≥12.5 mg/kg i.p., and a concentration ≥0.52 μM in water compromises swimming performance in larval fathead minnow. In isolated ventricular cardiomyocytes, skeletal myotubes, and adult flexor digitorum brevis fibers TCS depresses electrically evoked ECC within ∼10-20 min. In myotubes, nanomolar to low micromolar TCS initially potentiates electrically evoked Ca(2+) transients followed by complete failure of ECC, independent of Ca(2+) store depletion or block of RyR1 channels. TCS also completely blocks excitation-coupled Ca(2+) entry. Voltage clamp experiments showed that TCS partially inhibits L-type Ca(2+) currents of cardiac and skeletal muscle, and [(3)H]PN200 binding to skeletal membranes is noncompetitively inhibited by TCS in the same concentration range that enhances [(3)H]ryanodine binding. TCS potently impairs orthograde and retrograde signaling between L-type Ca(2+) and RyR channels in skeletal muscle, and L-type Ca(2+) entry in cardiac muscle, revealing a mechanism by which TCS weakens cardiac and skeletal muscle contractility in a manner that may negatively impact muscle health, especially in susceptible populations.

  11. The evolutionary history of the development of the pelvic fin/hindlimb

    PubMed Central

    Don, Emily K; Currie, Peter D; Cole, Nicholas J

    2013-01-01

    The arms and legs of man are evolutionarily derived from the paired fins of primitive jawed fish. Few evolutionary changes have attracted as much attention as the origin of tetrapod limbs from the paired fins of ancestral fish. The hindlimbs of tetrapods are derived from the pelvic fins of ancestral fish. These evolutionary origins can be seen in the examination of shared gene and protein expression patterns during the development of pelvic fins and tetrapod hindlimbs. The pelvic fins of fish express key limb positioning, limb bud induction and limb outgrowth genes in a similar manner to that seen in hindlimb development of higher vertebrates. We are now at a point where many of the key players in the development of pelvic fins and vertebrate hindlimbs have been identified and we can now readily examine and compare mechanisms between species. This is yielding fascinating insights into how the developmental programme has altered during evolution and how that relates to anatomical change. The role of pelvic fins has also drastically changed over evolutionary history, from playing a minor role during swimming to developing into robust weight-bearing limbs. In addition, the pelvic fins/hindlimbs have been lost repeatedly in diverse species over evolutionary time. Here we review the evolution of pelvic fins and hindlimbs within the context of the changes in anatomical structure and the molecular mechanisms involved. PMID:22913749

  12. Increased susceptibility to Pseudomonas aeruginosa infection under hindlimb-unloading conditions

    NASA Technical Reports Server (NTRS)

    Aviles, Hernan; Belay, Tesfaye; Fountain, Kimberly; Vance, Monique; Sonnenfeld, Gerald

    2003-01-01

    It has been reported that spaceflight conditions alter the immune system and resistance to infection [Belay T, Aviles H, Vance M, Fountain K, and Sonnenfeld G. J Allergy Clin Immunol 170: 262-268, 2002; Hankins WR and Ziegelschmid JF. In: Biomedical Results of Apollo. Washington, DC: NASA, 1975, p. 43-81. (NASA Spec. Rep. SP-368)]. Ground-based models, including the hindlimb-unloading model, have become important tools for increasing understanding of how spaceflight conditions can influence physiology. The objective of the present study was to determine the effect of hindlimb unloading on the susceptibility of mice to Pseudomonas aeruginosa infection. Hindlimb-unloaded and control mice were subcutaneously infected with 1 LD50 of P. aeruginosa. Survival, bacterial organ load, and antibody and corticosterone levels were compared among the groups. Hindlimb unloading had detrimental effects for infected mice. Animals in the hindlimb-unloaded group, compared with controls, 1). showed significantly increased mortality and reduced time to death, 2). had increased levels of corticosterone, and 3). were much less able to clear bacteria from the organs. These results suggest that hindlimb unloading may induce the production of corticosterone, which may play a critical role in the modulation of the immune system leading to increased susceptibility to P. aeruginosa infection.

  13. Increased susceptibility to Pseudomonas aeruginosa infection under hindlimb-unloading conditions.

    PubMed

    Aviles, Hernan; Belay, Tesfaye; Fountain, Kimberly; Vance, Monique; Sonnenfeld, Gerald

    2003-07-01

    It has been reported that spaceflight conditions alter the immune system and resistance to infection [Belay T, Aviles H, Vance M, Fountain K, and Sonnenfeld G. J Allergy Clin Immunol 170: 262-268, 2002; Hankins WR and Ziegelschmid JF. In: Biomedical Results of Apollo. Washington, DC: NASA, 1975, p. 43-81. (NASA Spec. Rep. SP-368)]. Ground-based models, including the hindlimb-unloading model, have become important tools for increasing understanding of how spaceflight conditions can influence physiology. The objective of the present study was to determine the effect of hindlimb unloading on the susceptibility of mice to Pseudomonas aeruginosa infection. Hindlimb-unloaded and control mice were subcutaneously infected with 1 LD50 of P. aeruginosa. Survival, bacterial organ load, and antibody and corticosterone levels were compared among the groups. Hindlimb unloading had detrimental effects for infected mice. Animals in the hindlimb-unloaded group, compared with controls, 1). showed significantly increased mortality and reduced time to death, 2). had increased levels of corticosterone, and 3). were much less able to clear bacteria from the organs. These results suggest that hindlimb unloading may induce the production of corticosterone, which may play a critical role in the modulation of the immune system leading to increased susceptibility to P. aeruginosa infection. PMID:12626488

  14. Different forms of impairment of the fore-hindlimb coordination after partial spinal lesions in cats.

    PubMed

    Górska, T; Bem, T; Majczyński, H; Zmysłowski, W

    1996-01-01

    Effects of large low thoracic (T10-T11) partial spinal lesions involving either the ventral quadrants of the spinal cord and, to a different extent the dorsolateral funiculi, or different extent of the lateral funiculi and/or the dorsal columns, on the fore-hindlimb coordination were examined in cats walking overground at moderate speeds. In both groups of operated cats, except those in which the lesion was essentially confined to dorsal columns, three different forms of impairment of fore-hindlimb coordination were observed, depending on the extent of lesion: (1) a change of locomotion towards pacing with preservation of the equality rhythms in the fore- and the hindlimbs; (2) episodes of fore- and hindlimb rhythm dissociation and (3) a permanent dissociation of the fore- and hindlimb rhythms. A comparison of the results obtained in these two groups of operated cats points to the more important role played by the lateral funiculi, than by other parts of the spinal white matter, in controlling the fore-hindlimb coordination in cats.

  15. The hindlimb unloading rat model: literature overview, technique update and comparison with space flight data

    NASA Technical Reports Server (NTRS)

    Morey-Holton, Emily; Globus, Ruth K.; Kaplansky, Alexander; Durnova, Galina

    2005-01-01

    The hindlimb unloading rodent model is used extensively to study the response of many physiological systems to certain aspects of space flight, as well as to disuse and recovery from disuse for Earth benefits. This chapter describes the evolution of hindlimb unloading, and is divided into three sections. The first section examines the characteristics of 1064 articles using or reviewing the hindlimb unloading model, published between 1976 and April 1, 2004. The characteristics include number of publications, journals, countries, major physiological systems, method modifications, species, gender, genetic strains and ages of rodents, experiment duration, and countermeasures. The second section provides a comparison of results between space flown and hindlimb unloading animals from the 14-day Cosmos 2044 mission. The final section describes modifications to hindlimb unloading required by different experimental paradigms and a method to protect the tail harness for long duration studies. Hindlimb unloading in rodents has enabled improved understanding of the responses of the musculoskeletal, cardiovascular, immune, renal, neural, metabolic, and reproductive systems to unloading and/or to reloading on Earth with implications for both long-duration human space flight and disuse on Earth.

  16. Deoxypyridinoline in the Urine of Rats with Unloaded Hindlimbs

    NASA Technical Reports Server (NTRS)

    Arnaud, Sara B.; Navidi, M.; Wren, J.; Holton, Emily M. (Technical Monitor)

    1997-01-01

    The urinary excretion of deoxypyridinoline (U-Dpd), a nonreducible collagen crosslink in bone released by osteoclastic activity, is thought to be an accurate marker of bone resorption. The role of increased resorption in the osteopenia of a space flight model which unloads the hindlimbs by suspending the tail is controversial. To assess skeletal resorption in the model we measured U-Dpd (Pyrilinks-D, Metro Biosystems, Inc.) in serial 24 hour urine specimens collected from 250 a (Y) and 450 a (M) male rats with unloaded hindlimbs for four weeks. Both groups of rats were fed AIN76 diets with calcium restricted to 0.2% in Y and to 0.1 % in M. Blood was obtained after 28 days for parathyroid hormone (PTH), 1,25-dihydroxyvitamin D (1,25-D) and alkaline phosphatase (Alkptase). Basal U-Dpd was higher and more variable in Y than M (475+/-200 vs 67+/-9, nM/mM creatinine, p<.001). Repeated measures ANOVA in Y revealed decreases in U-Dpd, 36% in control (C) and 24% in unloaded (S) rats (p<.005). There was a nadir in YS on the 14th day not observed in YC (p<.05). U-Dpd in MC showed no change, but increased in MS by the 14th day and remained elevated. At the end of the experiment, body weights in both Y and M were less in S than C (337+/-16 vs 306+/-12g and 485+/-10 vs 461+/-6g, p=.002). Bill was inversely related to U-Dpd only in M (r=0.699, p=.024). PTH, similar in C and S in Y (52+/-15 vs 42+/-7pg/ml, NS) and M (68+/-13 vs 61+/-12, NS), was unrelated to U-Dpd. 1,25-D tended toward higher values in YC than YS (197+/-103 vs 119+/-30, NS) and correlated with U-Dpd (0.773, p=.015). Alkptase, 1.3 times higher in Y than M, was similar in C and S at the end of unloading. These findings indicate that bone resorption, as reflected by U-Dpd, is suppressed in young and stimulated in mature rats exposed to a space flight model. U-Dpd reflects reduced growth from the diet change in young control and experimental rats and loss of Bill in mature animals exposed to the space flight model, 2

  17. Calcium balance in mature male rats with unloaded hindlimbs

    NASA Technical Reports Server (NTRS)

    Navidi, Meena; Evans, Juliann; Wolinsky, Ira; Arnaud, Sara B.

    2004-01-01

    BACKGROUND: Calcium balances, regulated by the calcium endocrine system, are negative during spaceflight but have not been reported in flight simulation models using fully mature small animals. METHODS: We conducted two calcium (Ca) balance studies in 6-mo-old male rats exposed to a model that unloads the hindlimbs (HU) for 4 wk. Control (C) and HU rats were fed diets with 0.5% Ca in the first and 0.1% Ca in the second study. Housing in metabolic cages enabled daily food and water intake measurements as well as collections of urine and fecal specimens. At necropsy, blood was obtained for measures of Ca-regulating hormones. RESULTS: Both C and HU rats adjusted to housing and diets with decreases in body weight and negative Ca balances during the first week of each experiment. Thereafter, averages of Ca balances were more negative in the unloaded rats than controls: -8.1 vs. -1.6 mg x d(-1) in rats fed 0.5% (p < 0.05). This difference was not due to urinary Ca excretion since it was lower in HU than C rats (1.27 +/- 0.51 mg x d(-1) vs. 2.35 +/- 0.82 mg x d(-1), p < 0.05). Fecal Ca in HU rats exceeded dietary Ca by 4-7%, Restricting dietary Ca to 0.1% was followed by an increase in serum 1,25-dihydroxyvitamin D (1,25-D) and greater intestinal Ca absorption than in rats fed 0.5% Ca. Ca balances in rats fed 0.1% Ca were also more negative in HU than C rats (-2.4 vs. -0.03 mg x d(-1), p < 0.05). Parathyroid hormone (PTH) was suppressed and 1,25-D increased in HU rats fed 0.5% Ca. C rats fed 0.1% Ca had increased PTH and 1,25-D was the same as in the HU group. CONCLUSION: After adaptation, Ca balances were more negative in mature male rats with unloaded hindlimbs than controls, an effect from increased secretion and loss of endogenous fecal Ca associated with increased 1,25-D in Ca-replete and Ca-restricted rats.

  18. Dynamic diffusion tensor measurements in muscle tissue using Single Line Multiple Echo Diffusion Tensor Acquisition Technique at 3T

    PubMed Central

    Baete, Steven H.; Cho, Gene; Sigmund, Eric E.

    2015-01-01

    When diffusion biomarkers display transient changes, i.e. in muscle following exercise, traditional diffusion tensor imaging (DTI) methods lack temporal resolution to resolve the dynamics. This paper presents an MRI method for dynamic diffusion tensor acquisitions on a clinical 3T scanner. This method, SL-MEDITATE (Single Line Multiple Echo Diffusion Tensor Acquisition Technique) achieves a high temporal resolution (4s) (1) by rapid diffusion encoding through the acquisition of multiple echoes with unique diffusion sensitization and (2) by limiting the readout to a single line volume. The method is demonstrated in a rotating anisotropic phantom, in a flow phantom with adjustable flow speed, and in in vivo skeletal calf muscle of healthy volunteers following a plantar flexion exercise. The rotating and flow-varying phantom experiments show that SL-MEDITATE correctly identifies the rotation of the first diffusion eigenvector and the changes in diffusion tensor parameter magnitudes, respectively. Immediately following exercise, the in vivo mean diffusivity (MD) time-courses show, before the well-known increase, an initial decrease which is not typically observed in traditional DTI. In conclusion, SL-MEDITATE can be used to capture transient changes in tissue anisotropy in a single line. Future progress might allow for dynamic DTI when combined with appropriate k-space trajectories and compressed sensing reconstruction. PMID:25900166

  19. Impaired Axonal Na+ Current by Hindlimb Unloading: Implication for Disuse Neuromuscular Atrophy

    PubMed Central

    Banzrai, Chimeglkham; Nodera, Hiroyuki; Kawarai, Toshitaka; Higashi, Saki; Okada, Ryo; Mori, Atsuko; Shimatani, Yoshimitsu; Osaki, Yusuke; Kaji, Ryuji

    2016-01-01

    This study aimed to characterize the excitability changes in peripheral motor axons caused by hindlimb unloading (HLU), which is a model of disuse neuromuscular atrophy. HLU was performed in normal 8-week-old male mice by fixing the proximal tail by a clip connected to the top of the animal's cage for 3 weeks. Axonal excitability studies were performed by stimulating the sciatic nerve at the ankle and recording the compound muscle action potential (CMAP) from the foot. The amplitudes of the motor responses of the unloading group were 51% of the control amplitudes [2.2 ± 1.3 mV (HLU) vs. 4.3 ± 1.2 mV (Control), P = 0.03]. Multiple axonal excitability analysis showed that the unloading group had a smaller strength-duration time constant (SDTC) and late subexcitability (recovery cycle) than the controls [0.075 ± 0.01 (HLU) vs. 0.12 ± 0.01 (Control), P < 0.01; 5.4 ± 1.0 (HLU) vs. 10.0 ± 1.3 % (Control), P = 0.01, respectively]. Three weeks after releasing from HLU, the SDTC became comparable to the control range. Using a modeling study, the observed differences in the waveforms could be explained by reduced persistent Na+ currents along with parameters related to current leakage. Quantification of RNA of a SCA1A gene coding a voltage-gated Na+ channel tended to be decreased in the sciatic nerve in HLU. The present study suggested that axonal ion currents are altered in vivo by HLU. It is still undetermined whether the dysfunctional axonal ion currents have any pathogenicity on neuromuscular atrophy or are the results of neural plasticity by atrophy. PMID:26909041

  20. Impaired Axonal Na(+) Current by Hindlimb Unloading: Implication for Disuse Neuromuscular Atrophy.

    PubMed

    Banzrai, Chimeglkham; Nodera, Hiroyuki; Kawarai, Toshitaka; Higashi, Saki; Okada, Ryo; Mori, Atsuko; Shimatani, Yoshimitsu; Osaki, Yusuke; Kaji, Ryuji

    2016-01-01

    This study aimed to characterize the excitability changes in peripheral motor axons caused by hindlimb unloading (HLU), which is a model of disuse neuromuscular atrophy. HLU was performed in normal 8-week-old male mice by fixing the proximal tail by a clip connected to the top of the animal's cage for 3 weeks. Axonal excitability studies were performed by stimulating the sciatic nerve at the ankle and recording the compound muscle action potential (CMAP) from the foot. The amplitudes of the motor responses of the unloading group were 51% of the control amplitudes [2.2 ± 1.3 mV (HLU) vs. 4.3 ± 1.2 mV (Control), P = 0.03]. Multiple axonal excitability analysis showed that the unloading group had a smaller strength-duration time constant (SDTC) and late subexcitability (recovery cycle) than the controls [0.075 ± 0.01 (HLU) vs. 0.12 ± 0.01 (Control), P < 0.01; 5.4 ± 1.0 (HLU) vs. 10.0 ± 1.3 % (Control), P = 0.01, respectively]. Three weeks after releasing from HLU, the SDTC became comparable to the control range. Using a modeling study, the observed differences in the waveforms could be explained by reduced persistent Na(+) currents along with parameters related to current leakage. Quantification of RNA of a SCA1A gene coding a voltage-gated Na(+) channel tended to be decreased in the sciatic nerve in HLU. The present study suggested that axonal ion currents are altered in vivo by HLU. It is still undetermined whether the dysfunctional axonal ion currents have any pathogenicity on neuromuscular atrophy or are the results of neural plasticity by atrophy. PMID:26909041

  1. Temporal extracellular matrix adaptations in ligament during wound healing and hindlimb unloading.

    PubMed

    Martinez, D A; Vailas, A C; Vanderby, R; Grindeland, R E

    2007-10-01

    Previous data from spaceflight studies indicate that injured muscle and bone heal slowly and abnormally compared with ground controls, strongly suggesting that ligaments or tendons may not repair optimally as well. Thus the objective of this study was to investigate the biochemical and molecular gene expression of the collagen extracellular matrix in response to medial collateral ligament (MCL) injury repair in hindlimb unloaded (HLU) rodents. Male rats were assigned to 3- and 7-wk treatment groups with three subgroups each: sham control, ambulatory healing (Amb-healing), and HLU-healing groups. Amb- and HLU-healing animals underwent bilateral surgical transection of their MCLs, whereas control animals were subjected to sham surgeries. All surgeries were performed under isoflurane anesthesia. After 3 wk or 7 wk of HLU, rats were euthanized and MCLs were surgically isolated and prepared for molecular or biochemical analyses. Hydroxyproline concentration and hydroxylysylpyridinoline collagen cross-link contents were measured by HPLC and showed a substantial decrement in surgical groups. MCL tissue cellularity, quantified by DNA content, remained significantly elevated in all HLU-healing groups vs. Amb-healing groups. MCL gene expression of collagen type I, collagen type III, collagen type V, fibronectin, decorin, biglycan, lysyl oxidase, matrix metalloproteinase-2, and tissue inhibitor of matrix metalloproteinase-1, measured by real-time quantitative PCR, demonstrated differential expression in the HLU-healing groups compared with Amb-healing groups at both the 3- and 7-wk time points. Together, these data suggest that HLU affects dense fibrous connective tissue wound healing and confirms previous morphological and biomechanical data that HLU inhibits the ligament repair processes.

  2. A Cretaceous terrestrial snake with robust hindlimbs and a sacrum.

    PubMed

    Apesteguía, Sebastián; Zaher, Hussam

    2006-04-20

    It has commonly been thought that snakes underwent progressive loss of their limbs by gradual diminution of their use. However, recent developmental and palaeontological discoveries suggest a more complex scenario of limb reduction, still poorly documented in the fossil record. Here we report a fossil snake with a sacrum supporting a pelvic girdle and robust, functional legs outside the ribcage. The new fossil, from the Upper Cretaceous period of Patagonia, fills an important gap in the evolutionary progression towards limblessness because other known fossil snakes with developed hindlimbs, the marine Haasiophis, Pachyrhachis and Eupodophis, lack a sacral region. Phylogenetic analysis shows that the new fossil is the most primitive (basal) snake known and that all other limbed fossil snakes are closer to the more advanced macrostomatan snakes, a group including boas, pythons and colubroids. The new fossil retains several features associated with a subterranean or surface dwelling life that are also present in primitive extant snake lineages, supporting the hypothesis of a terrestrial rather than marine origin of snakes.

  3. Hamiltonian Dynamics of a Forced Two-Degree-of-Freedom Arm with Viscoelastic Muscles Executing Planned Motions

    NASA Astrophysics Data System (ADS)

    Patra, Sayan; Ojakangas, Greg; Chase, Andrew; Chakrabarti, Anish; Sivils, Dalton; Johnson, Evan; Barrett, Kiefer; North, Mason; Julian, Preston

    2012-02-01

    In order to improve our understanding of how the brain controls the human arm both in the presence and absence of gravity, we have developed a two-degree-of-freedom robotic arm which is driven by six servo-actuated viscoelastic muscles. The computer-controlled servos mimic the contractive action of the sarcomeres in actual muscles, sections of elastic tubing represent the elastic behavior of actual muscles, while the behavior of tendons is represented by inelastic strings. The servos receive instructions to move from the visual C++ platform in the computer and the actual motion of the arm is recorded with optical encoders built into each joint axis. This experiment is a purely feed-forward system, and our goal is to determine whether our equations of motion, formulated using Hamiltonian dynamics, when numerically integrated, will predict the observed motion of the arm within experimental uncertainties. Our research was selected as one of 12 teams chosen nationwide as part of NASA Grant Us Space Reduced Gravity Program, to fly and perform experiments aboard NASA's Weightless Wonder aircraft in Summer 2011.

  4. 1α,25-Dihydroxyvitamin D3 Regulates Mitochondrial Oxygen Consumption and Dynamics in Human Skeletal Muscle Cells.

    PubMed

    Ryan, Zachary C; Craig, Theodore A; Folmes, Clifford D; Wang, Xuewei; Lanza, Ian R; Schaible, Niccole S; Salisbury, Jeffrey L; Nair, K Sreekumaran; Terzic, Andre; Sieck, Gary C; Kumar, Rajiv

    2016-01-15

    Muscle weakness and myopathy are observed in vitamin D deficiency and chronic renal failure, where concentrations of the active vitamin D3 metabolite, 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3), are low. To evaluate the mechanism of action of 1α,25(OH)2D3 in skeletal muscle, we examined mitochondrial oxygen consumption, dynamics, and biogenesis and changes in expression of nuclear genes encoding mitochondrial proteins in human skeletal muscle cells following treatment with 1α,25(OH)2D3. The mitochondrial oxygen consumption rate (OCR) increased in 1α,25(OH)2D3-treated cells. Vitamin D3 metabolites lacking a 1α-hydroxyl group (vitamin D3, 25-hydroxyvitamin D3, and 24R,25-dihydroxyvitamin D3) decreased or failed to increase OCR. 1α-Hydroxyvitamin D3 did not increase OCR. In 1α,25(OH)2D3-treated cells, mitochondrial volume and branching and expression of the pro-fusion protein OPA1 (optic atrophy 1) increased, whereas expression of the pro-fission proteins Fis1 (fission 1) and Drp1 (dynamin 1-like) decreased. Phosphorylated pyruvate dehydrogenase (PDH) (Ser-293) and PDH kinase 4 (PDK4) decreased in 1α,25(OH)2D3-treated cells. There was a trend to increased PDH activity in 1α,25(OH)2D3-treated cells (p = 0.09). 83 nuclear mRNAs encoding mitochondrial proteins were changed following 1α,25(OH)2D3 treatment; notably, PDK4 mRNA decreased, and PDP2 mRNA increased. MYC, MAPK13, and EPAS1 mRNAs, which encode proteins that regulate mitochondrial biogenesis, were increased following 1α,25(OH)2D3 treatment. Vitamin D receptor-dependent changes in the expression of 1947 mRNAs encoding proteins involved in muscle contraction, focal adhesion, integrin, JAK/STAT, MAPK, growth factor, and p53 signaling pathways were observed following 1α,25(OH)2D3 treatment. Five micro-RNAs were induced or repressed by 1α,25(OH)2D3. 1α,25(OH)2D3 regulates mitochondrial function, dynamics, and enzyme function, which are likely to influence muscle strength. PMID:26601949

  5. 1α,25-Dihydroxyvitamin D3 Regulates Mitochondrial Oxygen Consumption and Dynamics in Human Skeletal Muscle Cells.

    PubMed

    Ryan, Zachary C; Craig, Theodore A; Folmes, Clifford D; Wang, Xuewei; Lanza, Ian R; Schaible, Niccole S; Salisbury, Jeffrey L; Nair, K Sreekumaran; Terzic, Andre; Sieck, Gary C; Kumar, Rajiv

    2016-01-15

    Muscle weakness and myopathy are observed in vitamin D deficiency and chronic renal failure, where concentrations of the active vitamin D3 metabolite, 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3), are low. To evaluate the mechanism of action of 1α,25(OH)2D3 in skeletal muscle, we examined mitochondrial oxygen consumption, dynamics, and biogenesis and changes in expression of nuclear genes encoding mitochondrial proteins in human skeletal muscle cells following treatment with 1α,25(OH)2D3. The mitochondrial oxygen consumption rate (OCR) increased in 1α,25(OH)2D3-treated cells. Vitamin D3 metabolites lacking a 1α-hydroxyl group (vitamin D3, 25-hydroxyvitamin D3, and 24R,25-dihydroxyvitamin D3) decreased or failed to increase OCR. 1α-Hydroxyvitamin D3 did not increase OCR. In 1α,25(OH)2D3-treated cells, mitochondrial volume and branching and expression of the pro-fusion protein OPA1 (optic atrophy 1) increased, whereas expression of the pro-fission proteins Fis1 (fission 1) and Drp1 (dynamin 1-like) decreased. Phosphorylated pyruvate dehydrogenase (PDH) (Ser-293) and PDH kinase 4 (PDK4) decreased in 1α,25(OH)2D3-treated cells. There was a trend to increased PDH activity in 1α,25(OH)2D3-treated cells (p = 0.09). 83 nuclear mRNAs encoding mitochondrial proteins were changed following 1α,25(OH)2D3 treatment; notably, PDK4 mRNA decreased, and PDP2 mRNA increased. MYC, MAPK13, and EPAS1 mRNAs, which encode proteins that regulate mitochondrial biogenesis, were increased following 1α,25(OH)2D3 treatment. Vitamin D receptor-dependent changes in the expression of 1947 mRNAs encoding proteins involved in muscle contraction, focal adhesion, integrin, JAK/STAT, MAPK, growth factor, and p53 signaling pathways were observed following 1α,25(OH)2D3 treatment. Five micro-RNAs were induced or repressed by 1α,25(OH)2D3. 1α,25(OH)2D3 regulates mitochondrial function, dynamics, and enzyme function, which are likely to influence muscle strength.

  6. Sensitivity of dynamic simulations of gait and dynamometer experiments to hill muscle model parameters of knee flexors and extensors.

    PubMed

    De Groote, F; Van Campen, A; Jonkers, I; De Schutter, J

    2010-07-20

    We assessed and compared sensitivities of dynamic simulations to musculotendon (MT) parameters for gait and dynamometer experiments. Our aim with this comparison was to investigate whether dynamometer experiments could provide information about MT-parameters that are important to reliably study MT-function during gait. This would mean that dynamometer experiments could be used to estimate these parameters. Muscle contribution to the joint torque (MT-torque) rather than relative MT-force primarily affects the resulting gait pattern and torque measured by the dynamometer. In contrast to recent studies, therefore, we assessed the sensitivity of the MT-torque, rather than the sensitivity of the relative MT-force. Based on sensitivity of the MT-torque to a parameter perturbation, MT-parameters of the knee flexors and extensors were classified in three categories: low, medium, and high. For gait, classification was based on the average sensitivity during a gait cycle. For isometric and isokinetic dynamometer experiments, classification was based on the highest sensitivity found in the experiments. The calculated muscle contributions to the knee torque during gait and dynamometer experiments had a high sensitivity to only a limited number of MT-parameters of the knee flexors and extensors, suggesting that not all MT-parameters need to be estimated. In general, the highest sensitivity was found for tendon slack length. However, for some muscles the sensitivity to the optimal fibre length or the maximal isometric muscle force was also high or medium. The classification of the individual MT-parameters for gait and dynamometer experiments was largely similar. We therefore conclude that dynamometer experiments provide information about MT-parameters important to reliably study MT-function during gait, so that subject-specific estimates of MT-parameters could be made based on dynamometer experiments.

  7. Single-stage dynamic reanimation of the smile in irreversible facial paralysis by free functional muscle transfer.

    PubMed

    Thiele, Jan; Bannasch, Holger; Stark, G Bjoern; Eisenhardt, Steffen U

    2015-03-01

    Unilateral facial paralysis is a common disease that is associated with significant functional, aesthetic and psychological issues. Though idiopathic facial paralysis (Bell's palsy) is the most common diagnosis, patients can also present with a history of physical trauma, infectious disease, tumor, or iatrogenic facial paralysis. Early repair within one year of injury can be achieved by direct nerve repair, cross-face nerve grafting or regional nerve transfer. It is due to muscle atrophy that in long lasting facial paralysis complex reconstructive methods have to be applied. Instead of one single procedure, different surgical approaches have to be considered to alleviate the various components of the paralysis. The reconstruction of a spontaneous dynamic smile with a symmetric resting tone is a crucial factor to overcome the functional deficits and the social handicap that are associated with facial paralysis. Although numerous surgical techniques have been described, a two-stage approach with an initial cross-facial nerve grafting followed by a free functional muscle transfer is most frequently applied. In selected patients however, a single-stage reconstruction using the motor nerve to the masseter as donor nerve is superior to a two-stage repair. The gracilis muscle is most commonly used for reconstruction, as it presents with a constant anatomy, a simple dissection and minimal donor site morbidity. Here we demonstrate the pre-operative work-up, the post-operative management, and precisely describe the surgical procedure of single-stage microsurgical reconstruction of the smile by free functional gracilis muscle transfer in a step by step protocol. We further illustrate common pitfalls and provide useful tips which should enable the reader to truly comprehend the procedure. We further discuss indications and limitations of the technique and demonstrate representative results.

  8. Circulating micrornas as potential biomarkers of muscle atrophy

    NASA Astrophysics Data System (ADS)

    Wang, Fei

    2016-07-01

    Noninvasive biomarkers with diagnostic value and prognostic applications have long been desired to replace muscle biopsy for muscle atrophy patients. Growing evidence indicates that circulating microRNAs are biomarkers to assess pathophysiological status. Here, we show that the medium levels of six muscle-specific miRNAs (miR-1/23a/206/133/499/208b, also known as myomiRs) were all elevated in the medium of starved C2C12 cell (P < 0.01). And, the level of miR-1 and miR-23a were all elevated in the serum of hindlimb unloaded mice (P < 0.01). miR-23a levels were negatively correlated with both muscle mass and muscle fiber cross section area in muscle atrophy patients, indicating that they might represent the degree of muscle atrophy. Collectively, our data indicated that circulating myomiRs could serve as promising biomarkers for muscle atrophy.

  9. Adaptive control for backward quadrupedal walking V. Mutable activation of bifunctional thigh muscles.

    PubMed

    Pratt, C A; Buford, J A; Smith, J L

    1996-02-01

    1. In this, the fifth article in a series to assess changes in posture, hindlimb dynamics, and muscle synergies associated with backward (BWD) quadrupedal walking, we compared the recruitment of three biarticular muscles of the cat's anterior thigh (anterior sartorius, SAa; medial sartorius, SAm; rectus femoris, RF) for forward (FWD) and BWD treadmill walking. Electromyography (EMG) records from these muscles, along with those of two muscles (semitendinosus, ST; anterior biceps femoris, ABF) studied previously in this series, were synchronized with kinematic data digitized from high-speed ciné film for unperturbed steps and steps in which a stumbling corrective reaction was elicited during swing. 2. During swing, the relative timing of EMG activity for the unifunctional SAm (hip and knee flexor) was similar for unperturbed steps of FWD and BWD walking. The SAm was active before paw lift off and remained active during most of swing (75%) for both forms of walking, but there was a marked decrease in EMG amplitude after paw off during BWD and not FWD swing. In contrast, the relative timing of EMG activity for the SAa and RF, two bifunctional muscles (hip flexors, knee extensors), was different for FWD and BWD swing. During FWD swing, the SAa and the RF (to a lesser extent) were coactive with the SAm; however, during BWD swing, the SAa and RF were active just before paw lift off and then inactive for the rest of swing until just before paw contact (see 3). Thus the swing-phase activity of the SAa and RF was markedly shorter for BWD than FWD swing. 3. Activity in SAa and RF was also different during FWD and BWD stance. The RF was consistently active from mid-to-late stance of FWD walking, and the SAa was also active during this period in some FWD steps. During the stance phase of BWD walking, however, the onset of activity in both muscles consistently shifted to early stance as both muscles became active just before paw contact (the E1 phase). Activity in RF

  10. Developmental basis for hind-limb loss in dolphins and origin of the cetacean bodyplan

    PubMed Central

    Thewissen, J. G. M.; Cohn, M. J.; Stevens, L. S.; Bajpai, S.; Heyning, J.; Horton, W. E.

    2006-01-01

    Among mammals, modern cetaceans (whales, dolphins, and porpoises) are unusual in the absence of hind limbs. However, cetacean embryos do initiate hind-limb bud development. In dolphins, the bud arrests and degenerates around the fifth gestational week. Initial limb outgrowth in amniotes is maintained by two signaling centers, the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA). Our data indicate that the cetacean hind-limb bud forms an AER and that this structure expresses Fgf8 initially, but that neither the AER nor Fgf8 expression is maintained. Moreover, Sonic hedgehog (Shh), which mediates the signaling activity of the ZPA, is absent from the dolphin hind-limb bud. We find that failure to establish a ZPA is associated with the absence of Hand2, an upstream regulator of Shh. Interpreting our results in the context of both the cetacean fossil record and the known functions of Shh suggests that reduction of Shh expression may have occurred ≈41 million years ago and led to the loss of distal limb elements. The total loss of Shh expression may account for the further loss of hind-limb elements that occurred near the origin of the modern suborders of cetaceans ≈34 million years ago. Integration of paleontological and developmental data suggests that hind-limb size was reduced by gradually operating microevolutionary changes. Long after locomotor function was totally lost, modulation of developmental control genes eliminated most of the hind-limb skeleton. Hence, macroevolutionary changes in gene expression did not drive the initial reduction in hind-limb size. PMID:16717186

  11. Muscle [phosphocreatine] dynamics following the onset of exercise in humans: the influence of baseline work-rate.

    PubMed

    Jones, Andrew M; Wilkerson, Daryl P; Fulford, Jonathan

    2008-02-01

    The kinetics of pulmonary O(2) uptake is known to be substantially slower when exercise is initiated from a baseline of lower-intensity exercise rather than from rest. However, it is not known whether putative intracellular regulators of mitochondrial respiration (and in particular the phosphocreatine concentration, [PCr]) show similar non-linearities in their response dynamics. The purpose of this study was therefore to investigate the influence of baseline metabolic rate on muscle [PCr] kinetics (as assessed using (31)P-magnetic resonance spectroscopy) following the onset of exercise. Seven male subjects completed 'step' tests to heavy-intensity exercise (80% of peak work-rate) from a resting baseline and also from a baseline of moderate-intensity exercise (40% of peak work-rate) using a single-leg knee-extensor ergometer situated inside the bore of a 1.5 T super-conducting magnet. The time constant describing the kinetics of the initial exponential-like fall in [PCr] was significantly different between rest-to-moderate (25 +/- 14 s), rest-to-heavy (48 +/- 11 s) and moderate-to-heavy exercise (95 +/- 40 s) (P < 0.05 for all comparisons). A delayed-onset 'slow component' in the [PCr] response was observed in all subjects during rest-to-heavy exercise, but was attenuated in the moderate-to-heavy exercise condition. These data indicate that muscle [PCr] kinetics does not conform to 'linear, first-order' behaviour during dynamic exercise, and thus have implications for understanding the regulation of muscle oxidative metabolism.

  12. Task-Dependent Intermuscular Motor Unit Synchronization between Medial and Lateral Vastii Muscles during Dynamic and Isometric Squats

    PubMed Central

    Mohr, Maurice; Nann, Marius; von Tscharner, Vinzenz; Eskofier, Bjoern; Nigg, Benno Maurus

    2015-01-01

    Purpose Motor unit activity is coordinated between many synergistic muscle pairs but the functional role of this coordination for the motor output is unclear. The purpose of this study was to investigate the short-term modality of coordinated motor unit activity–the synchronized discharge of individual motor units across muscles within time intervals of 5ms–for the Vastus Medialis (VM) and Lateralis (VL). Furthermore, we studied the task-dependency of intermuscular motor unit synchronization between VM and VL during static and dynamic squatting tasks to provide insight into its functional role. Methods Sixteen healthy male and female participants completed four tasks: Bipedal squats, single-leg squats, an isometric squat, and single-leg balance. Monopolar surface electromyography (EMG) was used to record motor unit activity of VM and VL. For each task, intermuscular motor unit synchronization was determined using a coherence analysis between the raw EMG signals of VM and VL and compared to a reference coherence calculated from two desynchronized EMG signals. The time shift between VM and VL EMG signals was estimated according to the slope of the coherence phase angle spectrum. Results For all tasks, except for singe-leg balance, coherence between 15–80Hz significantly exceeded the reference. The corresponding time shift between VM and VL was estimated as 4ms. Coherence between 30–60Hz was highest for the bipedal squat, followed by the single-leg squat and the isometric squat. Conclusion There is substantial short-term motor unit synchronization between VM and VL. Intermuscular motor unit synchronization is enhanced for contractions during dynamic activities, possibly to facilitate a more accurate control of the joint torque, and reduced during single-leg tasks that require balance control and thus, a more independent muscle function. It is proposed that the central nervous system scales the degree of intermuscular motor unit synchronization according to the

  13. Electrically evoked and voluntary maximal isometric tension in relation to dynamic muscle performance in elderly male subjects, aged 69 years.

    PubMed

    Davies, C T; White, M J; Young, K

    1983-01-01

    The dynamic performance and electrically evoked mechanical properties of elderly triceps surae muscle have been investigated in 9 men, aged 69 yr. Dynamic performance consisted of cycling on a force bicycle and a vertical jump off two feet from a force platform. The results showed that the time to peak tension (TPT) and half relaxation time (1/2 RT) were significantly greater (p less than 0.001) by 30 ms and 22 ms and the supramaximal twitch (Pt) and tetanic (20 Hz-P020) tensions and maximal voluntary contraction (MVC) were less by 45 N (-33%), 708 N (-49%), and 899 N (-43%) in the elderly compared with young male control subjects. On the force platform, the height jumped (Ht), maximal force exerted (P), take-off velocity (VT), net impulse (NI) and peak power output (W) were less by 18.6 cm, 173 N, 0.9 ms-1, 52 Ns and 1120 w respectively. Similar differences of power, force and velocity were observed on the force bicycle. The reduction of W in the elderly was associated with the contractile characteristics of the leg muscle. The loss of contractile speed and capacity to to generate force in old people was reflected in their inability to develop power during the performance of a maximal vertical jump and cycling.

  14. GH/IGF-I Transgene Expression on Muscle Homeostasis

    NASA Technical Reports Server (NTRS)

    Schwartz, Robert J.

    1999-01-01

    We propose to test the hypothesis that the growth hormone/ insulin like growth factor-I axis through autocrine/paracrine mechanisms may provide long term muscle homeostasis under conditions of prolonged weightlessness. As a key alternative to hormone replacement therapy, ectopic production of hGH, growth hormone releasing hormone (GHRH), and IGF-I will be studied for its potential on muscle mass impact in transgenic mice under simulated microgravity. Expression of either hGH or IGF-I would provide a chronic source of a growth-promoting protein whose biosynthesis or secretion is shut down in space. Muscle expression of the IGF-I transgene has demonstrated about a 20% increase in hind limb muscle mass over control nontransgenic litter mates. These recent experiments, also establish the utility of hind-limb suspension in mice as a workable model to study atrophy in weight bearing muscles. Thus, transgenic mice will be used in hind-limb suspension models to determine the role of GH/IGF-I on maintenance of muscle mass and whether concentric exercises might act in synergy with hormone treatment. As a means to engineer and ensure long-term protein production that would be workable in humans, gene therapy technology will be used by to monitor muscle mass preservation during hind-limb suspension, after direct intramuscular injection of a genetically engineered muscle-specific vector expressing GHRH. Effects of this gene-based therapy will be assessed in both fast twitch (medial gastrocnemius) and slow twitch muscle (soleus). End-points include muscle size, ultrastructure, fiber type, and contractile function, in normal animals, hind limb suspension, and reambutation.

  15. Robust internal elastic lamina fenestration in skeletal muscle arteries.

    PubMed

    Kirby, Brett S; Bruhl, Allison; Sullivan, Michelle N; Francis, Michael; Dinenno, Frank A; Earley, Scott

    2013-01-01

    Holes within the internal elastic lamina (IEL) of blood vessels are sites of fenestration allowing for passage of diffusible vasoactive substances and interface of endothelial cell membrane projections with underlying vascular smooth muscle. Endothelial projections are sites of dynamic Ca(2+) events leading to endothelium dependent hyperpolarization (EDH)-mediated relaxations and the activity of these events increase as vessel diameter decreases. We tested the hypothesis that IEL fenestration is greater in distal vs. proximal arteries in skeletal muscle, and is unlike other vascular beds (mesentery). We also determined ion channel protein composition within the endothelium of intramuscular and non-intramuscular skeletal muscle arteries. Popliteal arteries, subsequent gastrocnemius feed arteries, and first and second order intramuscular arterioles from rat hindlimb were isolated, cut longitudinally, fixed, and imaged using confocal microscopy. Quantitative analysis revealed a significantly larger total fenestration area in second and first order arterioles vs. feed and popliteal arteries (58% and 16% vs. 5% and 3%; N = 10 images/artery), due to a noticeably greater average size of holes (9.5 and 3.9 µm(2) vs 1.5 and 1.9 µm(2)). Next, we investigated via immunolabeling procedures whether proteins involved in EDH often embedded in endothelial cell projections were disparate between arterial segments. Specific proteins involved in EDH, such as inositol trisphosphate receptors, small and intermediate conductance Ca(2+)-activated K(+) channels, and the canonical (C) transient receptor potential (TRP) channel TRPC3 were present in both popliteal and first order intramuscular arterioles. However due to larger IEL fenestration in first order arterioles, a larger spanning area of EDH proteins is observed proximal to the smooth muscle cell plasma membrane. These observations highlight the robust area of fenestration within intramuscular arterioles and indicate that the

  16. Effects of N-acetylcysteine and pentoxifylline on remote lung injury in a rat model of hind-limb ischemia/reperfusion injury

    PubMed Central

    Takhtfooladi, Hamed Ashrafzadeh; Hesaraki, Saeed; Razmara, Foad; Takhtfooladi, Mohammad Ashrafzadeh; Hajizadeh, Hadi

    2016-01-01

    Objective : To investigate the effects of N-acetylcysteine (NAC) and pentoxifylline in a model of remote organ injury after hind-limb ischemia/reperfusion (I/R) in rats, the lungs being the remote organ system. Methods : Thirty-five male Wistar rats were assigned to one of five conditions (n = 7/group), as follows: sham operation (control group); hind-limb ischemia, induced by clamping the left femoral artery, for 2 h, followed by 24 h of reperfusion (I/R group); and hind-limb ischemia, as above, followed by intraperitoneal injection (prior to reperfusion) of 150 mg/kg of NAC (I/R+NAC group), 40 mg/kg of pentoxifylline (I/R+PTX group), or both (I/R+NAC+PTX group). At the end of the trial, lung tissues were removed for histological analysis and assessment of oxidative stress. Results : In comparison with the rats in the other groups, those in the I/R group showed lower superoxide dismutase activity and glutathione levels, together with higher malondialdehyde levels and lung injury scores (p < 0.05 for all). Interstitial inflammatory cell infiltration of the lungs was also markedly greater in the I/R group than in the other groups. In addition, I/R group rats showed various signs of interstitial edema and hemorrhage. In the I/R+NAC, I/R+PTX, and I/R+NAC+PTX groups, superoxide dismutase activity, glutathione levels, malondialdehyde levels, and lung injury scores were preserved (p < 0.05 for all). The differences between the administration of NAC or pentoxifylline alone and the administration of the two together were not significant for any of those parameters (p > 0.05 for all). Conclusions : Our results suggest that NAC and pentoxifylline both protect lung tissue from the effects of skeletal muscle I/R. However, their combined use does not appear to increase the level of that protection. PMID:26982035

  17. Effect of Hindlimb Unweighting on Single Soleus Fiber Maximal Shortening Velocity and ATPase Activity

    NASA Technical Reports Server (NTRS)

    McDonald, K. S.; Fitts, R. H.

    1993-01-01

    This study characterizes the time course of change in single soleus muscle fiber size and function elicited by hindlimb un weighting (HU) and analyzes the extent to which varying durations of HU altered maximal velocity of shortening (V(sub o)), myofibrillar adenosinetriphosphatase (ATPase), and relative content of slow and fast myosin in individual soleus fibers. After 1, 2, or 3 weeks of HU, soleus muscle bundles were prepared and stored in skinning solution at -20 C. Single fibers were isolated and mounted between a motor arm and a transducer, and fiber force, V(sub o), and ATPase activity were measured. Fiber myosin content was determined by one-dimensional sodium dodecyl sulfate- (SDS) polyacrylamide gel electrophoresis. After 1, 2, and 3 weeks of HU, soleus fibers exhibited a progressive reduction in fiber diameter (16, 22, and 42%, respectively) and peak force (42, 48, and 7%, respectively). Peak specific tension was significantly reduced after 1 week of HU (18%) and showed no further change in 2-3 weeks of HU. During 1 and 3 wk of HU, fiber V(sub o) and ATPase showed a significant increase. By 3 week, V(sub o) had increased from 1.32 +/- 0.04 to 2.94 +/- 0.17 fiber lengths/s and fiber ATPase from 291 +/- 16 to 1064 +/- 128 micro-M min(sub -1) mm(sub -3). The percent fibers expressing fast myosin heavy chain increased from 4% to 29% by 3 week of HU, and V(sub o) and ATPase activity within a fiber were highly correlated. However, a large population of fibers after 1, 2, and 3 weeks of HU showed increases in V(sub o) and ATPase but displayed the same myosin protein profile on SDS gels as control fibers. The mechanism eliciting increased fiber V(sub o) and ATPase activity was not obvious but may have been due to increases in fast myosin that went undetected on SDS gels and/or other factors unrelated to the myosin filament.

  18. Skeletal muscle microvascular oxygenation dynamics in heart failure: exercise training and nitric oxide-mediated function.

    PubMed

    Hirai, Daniel M; Copp, Steven W; Holdsworth, Clark T; Ferguson, Scott K; McCullough, Danielle J; Behnke, Bradley J; Musch, Timothy I; Poole, David C

    2014-03-01

    Chronic heart failure (CHF) impairs nitric oxide (NO)-mediated regulation of skeletal muscle O2 delivery-utilization matching such that microvascular oxygenation falls faster (i.e., speeds PO2mv kinetics) during increases in metabolic demand. Conversely, exercise training improves (slows) muscle PO2mv kinetics following contractions onset in healthy young individuals via NO-dependent mechanisms. We tested the hypothesis that exercise training would improve contracting muscle microvascular oxygenation in CHF rats partly via improved NO-mediated function. CHF rats (left ventricular end-diastolic pressure = 17 ± 2 mmHg) were assigned to sedentary (n = 11) or progressive treadmill exercise training (n = 11; 5 days/wk, 6-8 wk, final workload of 60 min/day at 35 m/min; -14% grade downhill running) groups. PO2mv was measured via phosphorescence quenching in the spinotrapezius muscle at rest and during 1-Hz twitch contractions under control (Krebs-Henseleit solution), sodium nitroprusside (SNP; NO donor; 300 μM), and N(G)-nitro-l-arginine methyl ester (L-NAME, nonspecific NO synthase blockade; 1.5 mM) superfusion conditions. Exercise-trained CHF rats had greater peak oxygen uptake and spinotrapezius muscle citrate synthase activity than their sedentary counterparts (p < 0.05 for both). The overall speed of the PO2mv fall during contractions (mean response time; MRT) was slowed markedly in trained compared with sedentary CHF rats (sedentary: 20.8 ± 1.4, trained: 32.3 ± 3.0 s; p < 0.05), and the effect was not abolished by L-NAME (sedentary: 16.8 ± 1.5, trained: 31.0 ± 3.4 s; p > 0.05). Relative to control, SNP increased MRT in both groups such that trained CHF rats had slower kinetics (sedentary: 43.0 ± 6.8, trained: 55.5 ± 7.8 s; p < 0.05). Improved NO-mediated function is not obligatory for training-induced improvements in skeletal muscle microvascular oxygenation (slowed PO2mv kinetics) following contractions onset in rats with CHF.

  19. The measurement and dynamic implications of thin filament lengths in heart muscle.

    PubMed Central

    Robinson, T F; Winegrad, S

    1979-01-01

    1. The lengths of the thin filaments in amphibian and mammalian cardiac muscle have been determined from electron micrographs of serial transverse sections. Thin filament lengths in frog atrial trabeculae range from 0.8 to greater than 1.3 micrometers, with a maximum possible error of 0.14--0.15 micrometer. In rat atrial tissue the span is from 0.6 to more than 1.1 micrometer, whereas in rat papillary muscle the breadth of the distribution is much narrower, from 0.9 to greater than 1.1 micrometer. Double overlap of thin filaments should, therefore, exist over a wide range of sarcomere lenghts. Thin filaments from opposite halves of a sarcomere accommodate each other by flexing up to an angle of about 2 degrees and moving from the trigonal position among the thick filaments to the centre of the region between two thick filaments. Such rearrangement probably contributes to the internal resistance to shortening in the muscle. 2. Except for the variation in thin filament lengths, the over-all morphology of the cardiac sarcomere is generally similar to that found in skeletal muscle. Thick filaments in heart muscle are uniform in length, and their profiles change along their lengths. They are generally round in the M band, triangular adjacent to the M band, round again in the overlap region, and either round or triangular near the tapered tips. The M bridges in rat cardiac tissue link neighbouring thick filaments to form a symmetric hexagonal array, whereas in the frog atrium, the M bridge connexions are incomplete and often form isolated triangular clusters. 3. Computed sarcomere length-developed tension curves were calculated using the thin filament length distributions and the assumptions basic to the sliding filament theory of muscle contraction. The curves for atrial tissue have plateau regions approximately as wide as the one-half micron variation in thin filament length. 4. Work done against the internal loads during systole may be stored as potential energy and

  20. Muscle protein and glycogen responses to recovery from hypogravity and unloading by tail-cast suspension

    NASA Technical Reports Server (NTRS)

    Henriksen, E. J.; Tischler, M. E.; Jacob, S.; Cook, P. H.

    1985-01-01

    Previous studies in this laboratory using the tail-bast hindlimb suspension model have shown that there are specific changes in protein and carbohydrate metabolism in the soleus muscle due to unloading. For example, 6 days of unloading caused a 27 percent decrease in mass and a 60 percent increse in glycogen content in the soleus muscle, while the extensor digitorum longus muscle was unaffected. Also, fresh tissue tyrosine and its in vitro release from the muscle are increased in the unloaded soleus, indicating that this condition causes a more negative protein balance. With these results in mind, studies to investigate the effect of hypogravity on protein and carbohydrate metabolism in a number of rat hindlimb muscles were carried out.

  1. Muscle protein and glycogen responses to recovery from hypogravity and unloading by tail-cast suspension

    NASA Technical Reports Server (NTRS)

    Henriksen, E. J.; Tischler, M. E.; Jacob, S.; Cook, P. H.

    1985-01-01

    Previous studies in this laboratory using the tail-bast hindlimb suspension model have shown that there are specific changes in protein and carbohydrate metabolism in the soleus muscle due to unloading. For example, 6 days of unloading caused a 27% decrease in mass and a 60% increase in glycogen content in the soleus muscle, while the extensor digitorum longus muscle was unaffected. Also, fresh tissue tyrosine and its in vitro release from the muscle are increased in the unloaded soleus, indicating that this condition causes a more negative protein balance. With these results in mind, studies to investigate the effect of hypogravity on protein and carbohydrate metabolism in a number of rat hindlimb muscles were carried out.

  2. Mechanical Signal Transduction in Countermeasures to Muscle Atrophy

    NASA Technical Reports Server (NTRS)

    Tidball, James G.; Chu, Amy (Technical Monitor)

    2002-01-01

    We have shown that modifications in muscle use result in changes in the expression and activity of calpains and nitric oxide synthase (NOS). Although muscle unloading for 10 days produced no change in the concentrations of calpain 1 or 2 and no change in calpain activation, muscle reloading produced a 90% increase in calpain 2 concentration. We developed an in vitro model to test our hypothesis that nitric oxide can inhibit cytoskeletal breakdown in skeletal muscle cells by inhibiting calpain cleavage of talin. Talin was selected because it is a well-characterized calpain substrate and it is codistributed with calpain in muscle cells. We found that intermittant loading during hindlimb suspension that is sufficient to prevent muscle mass loss that occurs during muscle unloading is also sufficient to prevent the decrease in NOS expression that normally occurs during hindlimb unloading. These findings indicate that therapeutics directed toward regulating the calpain/calpastatin system may be beneficial in preventing muscle mass loss in muscle injury, unloading and disease.

  3. Development of Sensory Receptors in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    DeSantis, Mark

    2000-01-01

    There were two major goals for my project. One was to examine the hindlimb walking pattern of offspring from the Flight dams as compared with offspring of the ground control groups from initiation of walking up to two months thereafter. This initial goal was subsequently modified so that additional developmental measures were taken (e.g. body weight, eye opening) as the progeny developed, and the study period was lengthened to eighty days. Also videotapes taken shortly after the pregnant Flight dams returned to Earth were scored for locomotor activity and compared to those for the Synchronous control dams at the same stage of pregnancy. The second goal was to examine skeletal muscle. Selected hindlimb skeletal muscles were to be identified, weighed, and examined for the presence and integrity of muscle receptors, (both muscle spindles and tendon organs), at the level of the light and electron microscope. Muscles were examined from rats that were at fetal (G20), newborn (postnatal day 1 or P1, where P1 = day of birth), and young adult (approx. P100) stages. At the present time data from only the last group of rats (i.e. P100) has been completely examined.

  4. Your Muscles

    MedlinePlus

    ... Homework? Here's Help White House Lunch Recipes Your Muscles KidsHealth > For Kids > Your Muscles Print A A ... and skeletal (say: SKEL-uh-tul) muscle. Smooth Muscles Smooth muscles — sometimes also called involuntary muscles — are ...

  5. A novel optical imaging system for investigating sarcomere dynamics in single skeletal muscle fibers

    NASA Astrophysics Data System (ADS)

    Panchangam, Appaji; Witte, Russell S.; Claflin, Dennis R.; O'Donnell, Matthew; Faulkner, John A.

    2006-02-01

    The protein substructure of skeletal muscle fibers forms a diffraction grating with repeating units, termed 'sarcomeres'. A laser scanning system is described that maps the lengths of sarcomeres (SL) and the widths of the first-order diffraction lines (DLW) of permeabilized single fibers in real-time. The apparatus translates a laser beam (λ = 670 nm and w 0 = ~75 μm) along the length of a fiber segment through 20 contiguous regions per sweep at 500 sweeps/s. The fiber segments (~1 mm long) were obtained from vastus lateralis muscles of humans by needle biopsy. During both passive stretches and maximum fixed-end activations, the mappings of SL and DLW of the fibers were extracted from the diffraction spectra. Heterogeneity of SLs was evaluated by computing the standard deviation ( σ SL) of the 20 SLs measured during a single sweep. Compared with the σ SL before a passive stretch, the increase of 5+/-0.5% in σ SL after the passive stretch, indicated differences in passive length-tension relationships along the fiber. In contrast, no change, ~0.5+/-0.1%, was observed in DLW. Within 10s after the fiber was returned to its initial length, the shape of the SL profile returned close to pre-stretch conditions ( σ SL = 1+/- 0.2%). Following maximum Ca 2+ - activation of the fiber, the heterogeneity of the steady state SLs increased greatly (DLW up by ~300% and σ SL up by ~100%). The scanning system provided high resolution tracking of sarcomere behavior single muscle fibers. Potential applications are for studies of the mechanisms of muscle fiber injury and injury propagation.

  6. Dynamics of Muscle Microcirculatory and Blood-myocyte O2 Flux During Contractions

    PubMed Central

    Poole, David C.; Copp, Steven W.; Hirai, Daniel M.; Musch, Timothy I.

    2011-01-01

    The O2 requirements of contracting skeletal muscle may increase 100-fold above rest. In 1919 August Krogh’s brilliant insights recognized the capillary as the principal site for this increased blood-myocyte O2 flux. Based on the premise that most capillaries did not sustain RBC flux at rest Krogh proposed that capillary recruitment (i.e., initiation of red blood cell (RBC) flux in previously non-flowing capillaries) increased the capillary surface area available for O2 flux and reduced mean capillary-to-mitochondrial diffusion distances. More modern experimental approaches reveal that most muscle capillaries may support RBC flux at rest. Thus, rather than contraction-induced capillary recruitment per se, increased RBC flux and hematocrit within already-flowing capillaries likely elevate perfusive and diffusive O2 conductances and hence blood-myocyte O2 flux. Additional surface area for O2 exchange is recruited but, crucially, this may occur along the length of already-flowing capillaries (i.e. longitudinal recruitment). Today, the capillary is still considered the principal site for O2 and substrate delivery to contracting skeletal muscle. Indeed, the presence of very low intramyocyte O2 partial pressures (PO2’s) and the absence of PO2 gradients, whilst refuting the relevance of diffusion distances, place an even greater importance on capillary hemodynamics. This emergent picture calls for a paradigm-shift in our understanding of the function of capillaries by de-emphasizing de novo ‘capillary recruitment.’ Diseases such as heart failure impair blood-myocyte O2 flux, in part, by decreasing the proportion of RBC-flowing capillaries. Knowledge of capillary function in healthy muscle is requisite for identification of pathology and efficient design of therapeutic treatments. PMID:21199399

  7. Sallimus and the dynamics of sarcomere assembly in Drosophila flight muscles.

    PubMed

    Orfanos, Zacharias; Leonard, Kevin; Elliott, Chris; Katzemich, Anja; Bullard, Belinda; Sparrow, John

    2015-06-19

    The Drosophila indirect flight muscles (IFM) can be used as a model for the study of sarcomere assembly. Here we use a transgenic line with a green fluorescent protein (GFP) exon inserted into the Z-disc-proximal portion of sallimus (Sls), also known as Drosophila titin, to observe sarcomere assembly during IFM development. Firstly, we confirm that Sls-GFP can be used in the heterozygote state without an obvious phenotype in IFM and other muscles. We then use Sls-GFP in the IFM to show that sarcomeres grow individually and uniformly throughout the fibre, growing linearly in length and in diameter. Finally, we show that limiting the amounts of Sls in the IFM using RNAi leads to sarcomeres with smaller Z-discs in their core, whilst the thick/thin filament lattice can form peripherally without a Z-disc. Thick filament preparations from those muscles show that although the Z-disc-containing core has thick filaments of a regular length, filaments from the peripheral lattice are longer and asymmetrical around the bare zone. Therefore, the Z-disc and Sls are required for thick filament length specification but not for the assembly of the thin/thick filament lattice.

  8. Genetic basis of hindlimb loss in a naturally occurring vertebrate model

    PubMed Central

    Don, Emily K.; de Jong-Curtain, Tanya A.; Doggett, Karen; Hall, Thomas E.; Heng, Benjamin; Badrock, Andrew P.; Winnick, Claire; Nicholson, Garth A.; Guillemin, Gilles J.; Currie, Peter D.; Hesselson, Daniel; Heath, Joan K.; Cole, Nicholas J.

    2016-01-01

    ABSTRACT Here we genetically characterise pelvic finless, a naturally occurring model of hindlimb loss in zebrafish that lacks pelvic fin structures, which are homologous to tetrapod hindlimbs, but displays no other abnormalities. Using a hybrid positional cloning and next generation sequencing approach, we identified mutations in the nuclear localisation signal (NLS) of T-box transcription factor 4 (Tbx4) that impair nuclear localisation of the protein, resulting in altered gene expression patterns during pelvic fin development and the failure of pelvic fin development. Using a TALEN-induced tbx4 knockout allele we confirm that mutations within the Tbx4 NLS (A78V; G79A) are sufficient to disrupt pelvic fin development. By combining histological, genetic, and cellular approaches we show that the hindlimb initiation gene tbx4 has an evolutionarily conserved, essential role in pelvic fin development. In addition, our novel viable model of hindlimb deficiency is likely to facilitate the elucidation of the detailed molecular mechanisms through which Tbx4 functions during pelvic fin and hindlimb development. PMID:26892237

  9. The combined effects of X-ray radiation and hindlimb suspension on bone loss

    PubMed Central

    Xu, Dan; Zhao, Xin; Li, Yi; Ji, Yinli; Zhang, Jiangyan; Wang, Jufang; Xie, Xiaodong; Zhou, Guangming

    2014-01-01

    Outer space is a complex environment with various phenomena that negatively affect bone metabolism, including microgravity and highly energized ionizing radiation. In the present study, we used four groups of male Wistar rats treated with or without four-week hindlimb suspension after 4 Gy of X-rays to test whether there is a combined effect for hindlimb suspension and X-ray radiation. We tested trabecular parameters and some cytokines of the bone as leading indicators of bone metabolism. The results showed that hindlimb suspension and X-ray radiation could cause a significant increase in bone loss. Hindlimb suspension caused a 56.6% bone loss (P = 0.036), while X-ray radiation caused a 30.7% (P = 0.041) bone loss when compared with the control group. The combined factors of hindlimb suspension and X-rays exerted a combined effect on bone mass, with a reduction of 64.8% (P = 0.003). PMID:24699002

  10. Analysis of responses to kallidin, DABK, and DAK in feline hindlimb vascular bed.

    PubMed

    Santiago, J A; Garrison, E A; Champion, H C; Smith, R E; Del Rio, O; Kadowitz, P J

    1995-12-01

    Responses to kallidin, des-Arg9-bradykinin (DABK), and des-Arg10-kallidin (DAK) were investigated in the hindlimb vascular bed of the cat under constant-flow conditions. Injections of kallidin, DABK, and DAK into the hindlimb perfusion circuit produced dose-dependent vasodilator responses in the hindlimb vascular bed. Vasodilator responses to kallidin and bradykinin (BK) were similar in magnitude and time course, and both peptides were approximately 100-fold more potent than DABK or DAK. Responses to kallidin were decreased by the kinin B2 antagonist, HOE 140, whereas responses to DABK and DAK were reduced by des-Arg9[Leu8]BK, a kinin B1-receptor antagonist. N omega-nitro-L-arginine methyl ester (L-NAME) reduced vasodilator responses to kallidin, DABK, and DAK, whereas meclofenamate, atropine, and U-37883A, a vascular selective ATP-sensitive K+ (K+ATP) channel-blocking agent, did not alter responses to the three peptides. These data suggest that both kinin B1 and B2 receptors are normally present in the hindlimb vascular bed. These data also suggest that kinin B1 and B2 receptor-mediated vasodilator responses are mediated by the release of nitric oxide and that the activation of K+ATP channels or muscarinic receptors, or the release of vasodilator prostaglandins play little if any role in mediating responses to kallidin, DABK, or DAK in the hindlimb vascular bed of the cat.

  11. Emergence of airway smooth muscle mechanical behavior through dynamic reorganization of contractile units and force transmission pathways.

    PubMed

    Brook, Bindi S

    2014-04-15

    Airway hyperresponsiveness (AHR) in asthma remains poorly understood despite significant research effort to elucidate relevant underlying mechanisms. In particular, a significant body of experimental work has focused on the effect of tidal fluctuations on airway smooth muscle (ASM) cells, tissues, lung slices, and whole airways to understand the bronchodilating effect of tidal breathing and deep inspirations. These studies have motivated conceptual models that involve dynamic reorganization of both cytoskeletal components as well as contractile machinery. In this article, a biophysical model of the whole ASM cell is presented that combines 1) crossbridge cycling between actin and myosin; 2) actin-myosin disconnectivity, under imposed length changes, to allow dynamic reconfiguration of "force transmission pathways"; and 3) dynamic parallel-to-serial transitions of contractile units within these pathways that occur through a length fluctuation. Results of this theoretical model suggest that behavior characteristic of experimentally observed force-length loops of maximally activated ASM strips can be explained by interactions among the three mechanisms. Crucially, both sustained disconnectivity and parallel-to-serial transitions are necessary to explain the nature of hysteresis and strain stiffening observed experimentally. The results provide strong evidence that dynamic rearrangement of contractile machinery is a likely mechanism underlying many of the phenomena observed at timescales associated with tidal breathing. This theoretical cell-level model captures many of the salient features of mechanical behavior observed experimentally and should provide a useful starting block for a bottom-up approach to understanding tissue-level mechanical behavior.

  12. Airway mechanics and methods used to visualize smooth muscle dynamics in vitro.

    PubMed

    Cooper, P R; McParland, B E; Mitchell, H W; Noble, P B; Politi, A Z; Ressmeyer, A R; West, A R

    2009-10-01

    Contraction of airway smooth muscle (ASM) is regulated by the physiological, structural and mechanical environment in the lung. We review two in vitro techniques, lung slices and airway segment preparations, that enable in situ ASM contraction and airway narrowing to be visualized. Lung slices and airway segment approaches bridge a gap between cell culture and isolated ASM, and whole animal studies. Imaging techniques enable key upstream events involved in airway narrowing, such as ASM cell signalling and structural and mechanical events impinging on ASM, to be investigated.

  13. Near-Infrared Optical Imaging Noninvasively Detects Acutely Damaged Muscle.

    PubMed

    Chrzanowski, Stephen M; Batra, Abhinandan; Lee-McMullen, Brittany; Vohra, Ravneet S; Forbes, Sean C; Jiang, Huabei; Vandenborne, Krista; Walter, Glenn A

    2016-10-01

    Muscle damage is currently assessed through methods such as muscle biopsy, serum biomarkers, functional testing, and imaging procedures, each with its own inherent limitations, and a pressing need for a safe, repeatable, inexpensive, and noninvasive modality to assess the state of muscle health remains. Our aim was to develop and assess near-infrared (NIR) optical imaging as a novel noninvasive method of detecting and quantifying muscle damage. An immobilization-reambulation model was used for inducing muscle damage and recovery in the lower hindlimbs in mice. Confirmation of muscle damage was obtained using in vivo indocyanine green-enhanced NIR optical imaging, magnetic resonance imaging, and ex vivo tissue analysis. The soleus of the immobilized-reambulated hindlimb was found to have a greater amount of muscle damage compared to that in the contralateral nonimmobilized limb, confirmed by in vivo indocyanine green-enhanced NIR optical imaging (3.86-fold increase in radiant efficiency), magnetic resonance imaging (1.41-fold increase in T2), and an ex vivo spectrophotometric assay of indocyanine green uptake (1.87-fold increase in normalized absorbance). Contrast-enhanced NIR optical imaging provides a sensitive, rapid, and noninvasive screening method that can be used for imaging and quantifying muscle damage and recovery in vivo. PMID:27565039

  14. Proteome dynamics during contractile and metabolic differentiation of bovine foetal muscle.

    PubMed

    Chaze, T; Meunier, B; Chambon, C; Jurie, C; Picard, B

    2009-07-01

    Contractile and metabolic properties of bovine muscles play an important role in meat sensorial quality, particularly tenderness. Earlier studies based on Myosin heavy chain isoforms analyses and measurements of glycolytic and oxidative enzyme activities have demonstrated that the third trimester of foetal life in bovine is characterized by contractile and metabolic differentiation. In order to complete this data and to obtain a precise view of this phase and its regulation, we performed a proteomic analysis of Semitendinosus muscle from Charolais foetuses analysed at three stages of the third trimester of gestation (180, 210 and 260 days). The results complete the knowledge of important changes in the profiles of proteins from metabolic and contractile pathways. They provide new insights about proteins such as Aldehyde dehydrogenase family, Enolase, Dihydrolipoyl dehydrogenase, Troponin T or Myosin light chains isoforms. These data have agronomical applications not only for the management of beef sensorial quality but also in medical context, as bovine myogenesis appears very similar to human one. PMID:22444818

  15. Airway smooth muscle dynamics: a common pathway of airway obstruction in asthma

    PubMed Central

    An, S.S.; Bai, T.R.; Bates, J.H.T.; Black, J.L.; Brown, R.H.; Brusasco, V.; Chitano, P.; Deng, L.; Dowell, M.; Eidelman, D.H.; Fabry, B.; Fairbank, N.J.; Ford, L.E.; Fredberg, J.J.; Gerthoffer, W.T.; Gilbert, S.H.; Gosens, R.; Gunst, S.J.; Halayko, A.J.; Ingram, R.H.; Irvin, C.G.; James, A.L.; Janssen, L.J.; King, G.G.; Knight, D.A.; Lauzon, A.M.; Lakser, O.J.; Ludwig, M.S.; Lutchen, K.R.; Maksym, G.N.; Martin, J.G.; Mauad, T.; McParland, B.E.; Mijailovich, S.M.; Mitchell, H.W.; Mitchell, R.W.; Mitzner, W.; Murphy, T.M.; Paré, P.D.; Pellegrino, R.; Sanderson, M.J.; Schellenberg, R.R.; Seow, C.Y.; Silveira, P.S.P.; Smith, P.G.; Solway, J.; Stephens, N.L.; Sterk, P.J.; Stewart, A.G.; Tang, D.D.; Tepper, R.S.; Tran, T.; Wang, L.

    2008-01-01

    Excessive airway obstruction is the cause of symptoms and abnormal lung function in asthma. As airway smooth muscle (ASM) is the effecter controlling airway calibre, it is suspected that dysfunction of ASM contributes to the pathophysiology of asthma. However, the precise role of ASM in the series of events leading to asthmatic symptoms is not clear. It is not certain whether, in asthma, there is a change in the intrinsic properties of ASM, a change in the structure and mechanical properties of the noncontractile components of the airway wall, or a change in the interdependence of the airway wall with the surrounding lung parenchyma. All these potential changes could result from acute or chronic airway inflammation and associated tissue repair and remodelling. Anti-inflammatory therapy, however, does not “cure” asthma, and airway hyperresponsiveness can persist in asthmatics, even in the absence of airway inflammation. This is perhaps because the therapy does not directly address a fundamental abnormality of asthma, that of exaggerated airway narrowing due to excessive shortening of ASM. In the present study, a central role for airway smooth muscle in the pathogenesis of airway hyperresponsiveness in asthma is explored. PMID:17470619

  16. Regulation of actin dynamics by WNT-5A: implications for human airway smooth muscle contraction

    PubMed Central

    Koopmans, Tim; Kumawat, Kuldeep; Halayko, Andrew J; Gosens, Reinoud

    2016-01-01

    A defining feature of asthma is airway hyperresponsiveness (AHR), which underlies the exaggerated bronchoconstriction response of asthmatics. The role of the airway smooth muscle (ASM) in AHR has garnered increasing interest over the years, but how asthmatic ASM differs from healthy ASM is still an active topic of debate. WNT-5A is increasingly expressed in asthmatic ASM and has been linked with Th2-high asthma. Due to its link with calcium and cytoskeletal remodelling, we propose that WNT-5A may modulate ASM contractility. We demonstrated that WNT-5A can increase maximum isometric tension in bovine tracheal smooth muscle strips. In addition, we show that WNT-5A is preferentially expressed in contractile human airway myocytes compared to proliferative cells, suggesting an active role in maintaining contractility. Furthermore, WNT-5A treatment drives actin polymerisation, but has no effect on intracellular calcium flux. Next, we demonstrated that WNT-5A directly regulates TGF-β1-induced expression of α-SMA via ROCK-mediated actin polymerization. These findings suggest that WNT-5A modulates fundamental mechanisms that affect ASM contraction and thus may be of relevance for AHR in asthma. PMID:27468699

  17. Erk1/2 MAPK and Caldesmon Differentially Regulate Podosome Dynamics in A7r5 Vascular Smooth Muscle Cells

    PubMed Central

    Gu, Zhizhan; Kordowska, Jolanta; Williams, Geoffrey L.; Wang, C.-L. Albert; Hai, Chi-Ming

    2007-01-01

    We tested the hypothesis that the MEK/Erk/caldesmon phosphorylation cascade regulates PKC-mediated podosome dynamics in A7r5 cells. We observed the phosphorylation of MEK, Erk and caldesmon, and their translocation to the podosomes upon phorbol dibutyrate (PDBu) stimulation, together with the nuclear translocation of phospho-MEK and phospho-Erk. After MEK inhibition by U0126, Erk translocated to the interconnected actin-rich columns but failed to translocate to the nucleus, suggesting that podosomes served as a site for Erk phosphorylation. The interconnected actin-rich columns in U0126-treated, PDBu-stimulated cells contained α-actinin, caldesmon, vinculin, and metalloproteinase-2. Caldesmon and vinculin became integrated with F-actin at the columns, in contrast to their typical location at the ring of podosomes. Live-imaging experiments suggested the growth of these columns from podosomes that were slow to disassemble. The observed modulation of podosome size and life time in A7r5 cells overexpressing wild-type and phosphorylation-deficient caldesmon-GFP mutants in comparison to untransfected cells suggests that caldesmon and caldesmon phosphorylation modulate podosome dynamics in A7r5 cells. These results suggest that Erk1/2 and caldesmon differentially modulate PKC-mediated formation and/or dynamics of podosomes in A7r5 vascular smooth muscle cells. PMID:17239373

  18. Erk1/2 MAPK and caldesmon differentially regulate podosome dynamics in A7r5 vascular smooth muscle cells

    SciTech Connect

    Gu Zhizhan; Kordowska, Jolanta; Williams, Geoffrey L.; Wang, C.-L. Albert; Hai, C.-M. . E-mail: Chi-Ming_Hai@brown.edu

    2007-03-10

    We tested the hypothesis that the MEK/Erk/caldesmon phosphorylation cascade regulates PKC-mediated podosome dynamics in A7r5 cells. We observed the phosphorylation of MEK, Erk and caldesmon, and their translocation to the podosomes upon phorbol dibutyrate (PDBu) stimulation, together with the nuclear translocation of phospho-MEK and phospho-Erk. After MEK inhibition by U0126, Erk translocated to the interconnected actin-rich columns but failed to translocate to the nucleus, suggesting that podosomes served as a site for Erk phosphorylation. The interconnected actin-rich columns in U0126-treated, PDBu-stimulated cells contained {alpha}-actinin, caldesmon, vinculin, and metalloproteinase-2. Caldesmon and vinculin became integrated with F-actin at the columns, in contrast to their typical location at the ring of podosomes. Live-imaging experiments suggested the growth of these columns from podosomes that were slow to disassemble. The observed modulation of podosome size and life time in A7r5 cells overexpressing wild-type and phosphorylation-deficient caldesmon-GFP mutants in comparison to untransfected cells suggests that caldesmon and caldesmon phosphorylation modulate podosome dynamics in A7r5 cells. These results suggest that Erk1/2 and caldesmon differentially modulate PKC-mediated formation and/or dynamics of podosomes in A7r5 vascular smooth muscle cells.

  19. Muscle-specific androgen receptor deletion shows limited actions in myoblasts but not in myofibers in different muscles in vivo.

    PubMed

    Rana, Kesha; Chiu, Maria W S; Russell, Patricia K; Skinner, Jarrod P; Lee, Nicole K L; Fam, Barbara C; Zajac, Jeffrey D; MacLean, Helen E

    2016-08-01

    The aim of this study was to investigate the direct muscle cell-mediated actions of androgens by comparing two different mouse lines. The cre-loxP system was used to delete the DNA-binding activity of the androgen receptor (AR) in mature myofibers (MCK mAR(ΔZF2)) in one model and the DNA-binding activity of the AR in both proliferating myoblasts and myofibers (α-actin mAR(ΔZF2)) in another model. We found that hind-limb muscle mass was normal in MCK mAR(ΔZF2) mice and that relative mass of only some hind-limb muscles was reduced in α-actin mAR(ΔZF2) mice. This suggests that myoblasts and myofibers are not the major cellular targets mediating the anabolic actions of androgens on male muscle during growth and development. Levator ani muscle mass was decreased in both mouse lines, demonstrating that there is a myofiber-specific effect in this unique androgen-dependent muscle. We found that the pattern of expression of genes including c-myc, Fzd4 and Igf2 is associated with androgen-dependent changes in muscle mass; therefore, these genes are likely to be mediators of anabolic actions of androgens. Further research is required to identify the major targets of androgen actions in muscle, which are likely to include indirect actions via other tissues.

  20. Equine laryngeal hemiplegia. Part IV. Muscle pathology.

    PubMed

    Cahill, J I; Goulden, B E

    1986-11-01

    This study confirmed that neurogenic muscle pathology exists in intrinsic laryngeal muscles supplied by the recurrent laryngeal nerves in horses subclinically and clinically affected with laryngeal hemiplegia. An important additional observation was the occurrence in three out of four laryngeal hemiplegic horses of neurogenic muscle changes in a hindlimb muscle, the extensor digitorum longus, a muscle supplied by another long peripheral nerve. This finding suggests that a polynenropathy exists in laryngeal hemiplegic horses, and supports the classification of this disease as a distal axonopathy. Comparison of the degree of pathology in the intrinsic laryngeal muscles and that of the recurrent laryngeal nerves innervating them, demonstrated a strong correlation between the extent of damage in the distal left recurrent laryngeal nerve and the overall degree of muscle pathology. The muscle damage in clinically affected horses is a reflection of the nerve damage present in the most distal portion of the recurrent laryngeal nerve. The more variable pathological changes found in proximal levels of the left and right recurrent laryngeal nerves probably reflects the ongoing nature of the pathological process affecting nerve fibres. The existence of a subclinically affected group of horses, the earliest involvement of an adductor, the left cricoarytenoideus lateralis muscle, and the presence of changes in the right intrinsic laryngeal muscles all confirmed the findings of previous workers.

  1. Pharmacological Inhibitors of the Proteosome in Atrophying Muscles

    NASA Technical Reports Server (NTRS)

    Goldberg, Alfred

    1999-01-01

    It is now clear that the marked loss of muscle mass that occurs with disuse, denervation or in many systemic diseases (cancer cachexia, sepsis, acidosis, various endocrine disorders) is due primarily to accelerated degradation of muscle proteins, especially myofibrillar components. Recent work primarily in Dr. Goldberg's laboratory had suggested that in these diverse conditions, the enhancement of muscle proteolysis results mainly from activation of the Ub-proteasome degradative pathway. In various experimental models of atrophy, rat muscles show a common series of changes indicative of activation of this pathway, including increases in MRNA for Ub and proteasome subunits, content of ubiquitinated proteins, and sensitivity to inhibitors of the proteasome. In order to understand the muscle atrophy seen in weightlessness, Dr. Goldberg's laboratory is collaborating with Dr. Baldwin in studies to define the changes in these parameters upon hind-limb suspension. Related experiments will explore the effects on this degradative system of exercise regimens and also of glucocorticoids, which are known to rise in space personnel and to promote muscle, especially in inactive muscles. The main goals will be: (A) to define the enzymatic changes leading to enhanced activity of the Ub-proteasome pathway in inactive muscles upon hind-limb suspension, and the effects on this system of exposure to glucocorticoids or exercise; and (B) to learn whether inhibitors of the Ub-proteasome pathway may be useful in retarding the excessive proteolysis in atrophying muscles. Using muscle extracts, Dr. Goldberg's group hopes to define the rate-limiting, enzymatic changes that lead to the accelerated Ub-conjugation and protein degradation. They have recently developed cell-free preparations from atrophying rat muscles, in which Ub-conjugation to muscle proteins is increased above control levels. Because these new preparations seem to reproduce the changes occurring in vivo, they will analyze in

  2. Developmental segregation of spinal networks driving axial- and hindlimb-based locomotion in metamorphosing Xenopus laevis.

    PubMed

    Combes, D; Merrywest, S D; Simmers, J; Sillar, K T

    2004-08-15

    Amphibian metamorphosis includes a complete reorganization of an organism's locomotory system from axial-based swimming in larvae to limbed propulsion in the young adult. At critical stages during this behavioural switch, larval and adult motor systems operate in the same animal, commensurate with a gradual and dynamic reconfiguration of spinal locomotor circuitry. To study this plasticity, we have developed isolated preparations of the spinal cord and brainstem from pre- to post-metamorphic stages of the amphibian Xenopus laevis, in which spinal motor output patterns expressed spontaneously or in the presence of NMDA correlate with locomotor behaviour in the freely swimming animal. Extracellular ventral root recordings along the spinal cord of pre-metamorphic tadpoles revealed motor output corresponding to larval axial swimming, whereas postmetamorphic animals expressed motor patterns appropriate for bilaterally synchronous hindlimb flexion-extension kicks. However, in vitro recordings from metamorphic climax stages, with the tail and the limbs both functional, revealed two distinct motor patterns that could occur either independently or simultaneously, albeit at very different frequencies. Activity at 0.5-1 Hz in lumbar ventral roots corresponded to bipedal extension-flexion cycles, while the second, faster pattern (2-5 Hz) recorded from tail ventral roots corresponded to larval-like swimming. These data indicate that at intermediate stages during metamorphosis separate networks, one responsible for segmentally organized axial locomotion and another for more localized appendicular rhythm generation, coexist in the spinal cord and remain functional after isolation in vitro. These preparations now afford the opportunity to explore the cellular basis of locomotor network plasticity and reconfiguration necessary for behavioural changes during development.

  3. Dynamics of a Planar Arm Model with Servo-regulated Viscoelastic Muscles in a Microgravity Environment

    NASA Astrophysics Data System (ADS)

    Durden, Jared

    2008-03-01

    We constructed a mechanical arm model consisting of a rigid upper arm and forearm which simulates vertical planar arm motion with two degrees of freedom: shoulder rotation and elbow rotation. Computer controlled servo-motors effect rotation of the elbow and shoulder joints through tensions incited in elastic materials which represent muscles. We predicted and then observed vertical planar arm motion in the laboratory under normal Earth gravity conditions, and on NASAs Weightless Wonder in near zero gravity conditions. Because the arm only has two degrees of freedom we were able to simulate near zero gravity in the laboratory and predict the subsequent motion by operating it in the horizontal plane. We will discuss results of the actual observed motion in these three environments, and compare them to the motion predicted based on the equations of motion. We will also discuss how the project was developed physically, mathematically, and electronically.

  4. An alternant method to the traditional NASA hindlimb unloading model in mice.

    PubMed

    Ferreira, J Andries; Crissey, Jacqueline M; Brown, Marybeth

    2011-03-10

    The Morey-Holton hindlimb unloading (HU) method is a widely accepted National Aeronautics and Space Administration (NASA) ground-based model for studying disuse-atrophy in rodents. Our study evaluated an alternant method to the gold-standard Morey-Holton HU tail-traction technique in mice. Fifty-four female mice (4-8 mo.) were HU for 14 days (n=34) or 28 days (n=20). Recovery from HU was assessed after 3 days of normal cage ambulation following HU (n=22). Aged matched mice (n=76) served as weight-bearing controls. Prior to HU a tail ring was formed with a 2-0 sterile surgical steel wire that was passed through the 5(th), 6(th), or 7(th) inter-vertebral disc space and shaped into a ring from which the mice were suspended. Vertebral location for the tail-ring was selected to appropriately balance animal body weight without interfering with defecation. We determined the success of this novel HU technique by assessing body weight before and after HU, degree of soleus atrophy, and adrenal mass following HU. Body weight of the mice prior to HU (24.3 ± 2.9g) did not significantly decline immediately after 14d of HU (22.7 ± 1.9g), 28d of HU (21.3 + 2.1g) or after 3 days recovery (24.0 ± 1.8g). Soleus muscle mass significantly declined (-39.1%, and -46.6%) following HU for 14 days and 28 days respectively (p<0.001). Following 3 days of recovery soleus mass significantly increased to 74% of control values. Adrenal weights of HU mice were not different compared to control mice. The success of our novel HU method is evidenced by the maintenance of animal body weight, comparable adrenal gland weights, and soleus atrophy following HU, corresponding to expected literature values. The primary advantages of this HU method include: 1) ease of tail examination during suspension; 2) decreased likelihood of cyanotic, inflamed, and/or necrotic tails frequently observed with tail-taping and HU; 3) no possibility of mice chewing the traction tape and coming out of the suspension

  5. Prostacyclin-producing human mesenchymal cells target H19 lncRNA to augment endogenous progenitor function in hindlimb ischaemia

    PubMed Central

    Deng, Yuxiao; Yang, Zhongwei; Terry, Toya; Pan, Su; Woodside, Darren G.; Wang, Jingxiong; Ruan, Kehe; Willerson, James T.; Dixon, Richard A. F.; Liu, Qi

    2016-01-01

    Promoting the paracrine effects of human mesenchymal stem cell (hMSC) therapy may contribute to improvements in patient outcomes. Here we develop an innovative strategy to enhance the paracrine effects of hMSCs. In a mouse hindlimb ischaemia model, we examine the effects of hMSCs in which a novel triple-catalytic enzyme is introduced to stably produce prostacyclin (PGI2-hMSCs). We show that PGI2-hMSCs facilitate perfusion recovery and enhance running capability as compared with control hMSCs or iloprost (a stable PGI2 analogue). Transplanted PGI2-hMSCs do not incorporate long term into host tissue, but rather they mediate host regeneration and muscle mass gain in a paracrine manner. Mechanistically, this involves long noncoding RNA H19 in promoting PGI2-hMSC-associated survival and proliferation of host progenitor cells under hypoxic conditions. Together, our data reveal the novel ability of PGI2-hMSCs to stimulate host regenerative processes and improve physical function by regulating long noncoding RNA in resident progenitor cells. PMID:27080438

  6. A 3D analysis of fore- and hindlimb motion during locomotion: comparison of overground and ladder walking in rats.

    PubMed

    Garnier, Cyril; Falempin, Maurice; Canu, Marie-Hélène

    2008-01-10

    The locomotor pattern, generated by the central pattern generator, is under the dependence of descending and peripheral pathways. The afferent feedback from peripheral receptors allows the animal to correct for disturbances that occur during walking, while supraspinal structures are important for locomotion in demanding situations such as ladder walking. Such walking, by regards to the control needed for accuracy of movements, is now widely used for description of consequences of nervous system dysfunction on motor performance. It is important to have a good knowledge of the changes in kinematic parameters according to walking conditions, since it might reflect different neural mechanisms. The aim of this work was to perform a 3D kinematic analysis of both hind- and forelimb during overground and ladder walking, to study qualitative and quantitative locomotor characteristics in different modes of locomotion. The analysis was performed on 5 rats. Movements of the right hind- and forelimb were evaluated using a 3D optical analyser, and EMG of the soleus and tibialis anterior muscles was synchronously recorded. Results indicate that kinematic and electromyographic characteristics of locomotion are dependent on the type of support. Changes were more obvious for hindlimb than for forelimb. Velocity, stride length and tibialis anterior burst duration were lower on ladder than on runway. In addition, during ladder walking, a protraction was noticed, rats bring their feet more rostral at the end of the swing phase. All these changes constitute an adaptive strategy to allow a better tactile activity with forelimbs and to avoid foot misplacement. PMID:17764759

  7. Morphological Dynamics of Mitochondria – A Special Emphasis on Cardiac Muscle Cells

    PubMed Central

    Hom, Jennifer; Sheu, Shey-Shing

    2010-01-01

    Mitochondria play a critical role in cellular energy metabolism, Ca2+ homeostasis, reactive oxygen species generation, apoptosis, aging, and development. Many recent publications have shown that a continuous balance of fusion and fission of these organelles is important in maintaining their proper function. Therefore, there is a steep correlation between the form and function of mitochondria. Many major proteins involved in mitochondrial fusion and fission have been identified in different cell types, including heart. However, the functional role of mitochondrial dynamics in the heart remains, for the most part, unexplored. In this review we will cover the recent field of mitochondrial dynamics and its physiological and pathological implications, with a particular emphasis on the experimental and theoretical basis of mitochondrial dynamics in the heart. PMID:19281816

  8. Behaviour of heart rate and electrical muscle activity in the simultaneous dynamic action of larger and smaller sets of muscles in the permanent performance threshold range.

    PubMed

    Weber, H; Naumann, H J; Jentsch, A; Tröger, B; Wunderlich, H

    1987-01-01

    This study was undertaken to assess more comprehensively and with greater differentiation the reduction in the absolute electrical muscle activity (aEA) determined by different investigations in the permanent performance threshold range of the cardiovascular system (HKS) by means of the behaviour of the aEA of the highly stressed leg muscles and little stressed forearm muscles. Six healthy, untrained male subjects operated a hand ergograph alone in one test, and, in four more tests, in combination with a constant bicycle ergometer load of 40, 60, 80, and 100 W, respectively. As a result of these tests, a relative reduction in aEA for the leg muscles and an absolute reduction in aEA for the forearm muscles could be identified in the permanent performance threshold range of the HKS. Therefore, aEA is also considered to be an indicator of general stress that can define the permanent performance threshold range of the HKS more completely. The reduction in aEA is probably an expression of a negative feedback from the cardiovascular system to the neuromuscular system induced by the central nervous system.

  9. Distinct α2 Na,K-ATPase membrane pools are differently involved in early skeletal muscle remodeling during disuse

    PubMed Central

    Kravtsova, Violetta V.; Petrov, Alexey M.; Matchkov, Vladimir V.; Bouzinova, Elena V.; Vasiliev, Alexander N.; Benziane, Boubacar; Zefirov, Andrey L.; Chibalin, Alexander V.; Heiny, Judith A.

    2016-01-01

    The Na,K-ATPase is essential for the contractile function of skeletal muscle, which expresses the α1 and α2 subunit isoforms of Na,K-ATPase. The α2 isozyme is predominant in adult skeletal muscles and makes a greater contribution in working compared with noncontracting muscles. Hindlimb suspension (HS) is a widely used model of muscle disuse that leads to progressive atrophy of postural skeletal muscles. This study examines the consequences of acute (6–12 h) HS on the functioning of the Na,K-ATPase α1 and α2 isozymes in rat soleus (disused) and diaphragm (contracting) muscles. Acute disuse dynamically and isoform-specifically regulates the electrogenic activity, protein, and mRNA content of Na,K-ATPase α2 isozyme in rat soleus muscle. Earlier disuse-induced remodeling events also include phospholemman phosphorylation as well as its increased abundance and association with α2 Na,K-ATPase. The loss of α2 Na,K-ATPase activity results in reduced electrogenic pump transport and depolarized resting membrane potential. The decreased α2 Na,K-ATPase activity is caused by a decrease in enzyme activity rather than by altered protein and mRNA content, localization in the sarcolemma, or functional interaction with the nicotinic acetylcholine receptors. The loss of extrajunctional α2 Na,K-ATPase activity depends strongly on muscle use, and even the increased protein and mRNA content as well as enhanced α2 Na,K-ATPase abundance at this membrane region after 12 h of HS cannot counteract this sustained inhibition. In contrast, additional factors may regulate the subset of junctional α2 Na,K-ATPase pool that is able to recover during HS. Notably, acute, low-intensity muscle workload restores functioning of both α2 Na,K-ATPase pools. These results demonstrate that the α2 Na,K-ATPase in rat skeletal muscle is dynamically and acutely regulated by muscle use and provide the first evidence that the junctional and extrajunctional pools of the α2 Na,K-ATPase are regulated

  10. Altered skeletal pattern of gene expression in response to spaceflight and hindlimb elevation

    NASA Technical Reports Server (NTRS)

    Bikle, D. D.; Harris, J.; Halloran, B. P.; Morey-Holton, E.

    1994-01-01

    Spaceflight leads to osteopenia, in part by inhibiting bone formation. Using an animal model (hindlimb elevation) that simulates the weightlessness of spaceflight, we and others showed a reversible inhibition of bone formation and bone mineralization. In this study, we have measured the mRNA levels of insulin-like growth factor I (IGF-I), IGF-I receptor (IGF-IR), alkaline phosphatase, and osteocalcin in the tibiae of rats flown aboard National Aeronautics and Space Administration Shuttle Flight STS-54 and compared the results with those obtained from their ground-based controls and from the bones of hindlimb-elevated animals. Spaceflight and hindlimb elevation transiently increase the mRNA levels for IGF-I, IGF-IR, and alkaline phosphatase but decrease the mRNA levels for osteocalcin. The changes in osteocalcin and alkaline phosphatase mRNA levels are consistent with a shift toward decreased maturation, whereas the rise in IGF-I and IGF-IR mRNA levels may indicate a compensatory response to the fall in bone formation. We conclude that skeletal unloading during spaceflight or hindlimb elevation resets the pattern of gene expression in the osteoblast, giving it a less mature profile.

  11. Decoding hindlimb movement for a brain machine interface after a complete spinal transection.

    PubMed

    Manohar, Anitha; Flint, Robert D; Knudsen, Eric; Moxon, Karen A

    2012-01-01

    Stereotypical locomotor movements can be made without input from the brain after a complete spinal transection. However, the restoration of functional gait requires descending modulation of spinal circuits to independently control the movement of each limb. To evaluate whether a brain-machine interface (BMI) could be used to regain conscious control over the hindlimb, rats were trained to press a pedal and the encoding of hindlimb movement was assessed using a BMI paradigm. Off-line, information encoded by neurons in the hindlimb sensorimotor cortex was assessed. Next neural population functions, or weighted representations of the neuronal activity, were used to replace the hindlimb movement as a trigger for reward in real-time (on-line decoding) in three conditions: while the animal could still press the pedal, after the pedal was removed and after a complete spinal transection. A novel representation of the motor program was learned when the animals used neural control to achieve water reward (e.g. more information was conveyed faster). After complete spinal transection, the ability of these neurons to convey information was reduced by more than 40%. However, this BMI representation was relearned over time despite a persistent reduction in the neuronal firing rate during the task. Therefore, neural control is a general feature of the motor cortex, not restricted to forelimb movements, and can be regained after spinal injury. PMID:23300606

  12. Hindlimb suspension diminishes femoral cross-sectional growth in the rat

    NASA Technical Reports Server (NTRS)

    van der Meulen, M. C.; Morey-Holton, E. R.; Carter, D. R.

    1995-01-01

    Growth, functional adaptation, and torsional strength were examined in the femora of 39-day-old male Sprague-Dawley rats subjected to hindlimb suspension for 0, 1, 2, 3, or 4 weeks and were compared with measurements for age-matched control animals. Our goal was to understand the effect of reduced loading on the normal age-related changes in femoral properties during growth. The control animals exhibited growth-related increases in all geometric and torsional properties of the femur. The mean body mass and femoral length of the hindlimb-suspended rats were similar to those of the controls throughout the experiment. Over 4 weeks, the femoral cross-sectional and torsional measurements from the hindlimb-suspended rats demonstrated increases in comparison with the basal values (+33% cross-sectional area, +64% polar moment of inertia, +67% ultimate torque, and +181% torsional rigidity), but the age-matched controls showed significantly greater growth-related increases (+71% cross-sectional area, +136% polar moment of inertia, +127% ultimate torque, and +367% torsional rigidity). The differences in femoral structural strength between the hindlimb-suspended animals and the age-matched controls were attributable to differences in altered cross-sectional geometry.

  13. Redox regulation of E3 ubiquitin ligases and their role in skeletal muscle atrophy.

    PubMed

    Olaso-Gonzalez, Gloria; Ferrando, Beatriz; Derbre, Frederic; Salvador-Pascual, Andrea; Cabo, Helena; Pareja-Galeano, Helios; Sabater-Pastor, Frederic; Gomez-Cabrera, Mari Carmen; Vina, Jose

    2014-10-01

    Muscle atrophy is linked to reactive oxygen species (ROS) production during hindlimb-unloading due, at least in part, to the activation of xanthine oxidase (XO). The major aim of our study was to determine the mechanism by which ROS cause muscle atrophy and its possible prevention by allopurinol, a well-known inhibitor of XO widely used in clinical practice, and indomethacin, a nonsteroidal anti-inflammatory drug. We studied the activation of p38 MAP Kinase and NF-?B pathways, and the expression of two E3 ubiquitin ligases involved in proteolysis, the Muscle atrophy F-Box (MAFb) and Muscle RING Finger-1 (MuRF-1). Male Wistar rats (3 mold) conditioned by 14 days of hindlimb unloading (n=18), with or without the treatment, were compared with freely ambulating controls (n=18). After the experimental intervention, soleus muscles were removed, weighted and analyzed to determine oxidative stress and inflammatory parameters. We found that hindlimb unloading induced a significant increase in XO activity in plasma (39%, p=0.001) and in the protein expression of CuZnSOD and Catalase in skeletal muscle. Inhibitionof XO partially prevented protein carbonylation, both in plasma and in soleus muscle, in the unloaded animals. The most relevant new fact reported is that allopurinol prevents soleus muscle atrophy by ~20% after hindlimb unloading. Combining allopurinol and indomethacin we found a further prevention in the atrophy process. This is mediated by the inhibition of the p38 MAPK-MAFbx and NF-?B -MuRF-1 pathways. Our data point out the potential benefit of allopurinol and indomethacin administration for bedridden, astronauts, sarcopenic and cachexic patients. PMID:26461377

  14. Dynamic bending of bionic flexible body driven by pneumatic artificial muscles(PAMs) for spinning gait of quadruped robot

    NASA Astrophysics Data System (ADS)

    Lei, Jingtao; Yu, Huangying; Wang, Tianmiao

    2016-01-01

    The body of quadruped robot is generally developed with the rigid structure. The mobility of quadruped robot depends on the mechanical properties of the body mechanism. It is difficult for quadruped robot with rigid structure to achieve better mobility walking or running in the unstructured environment. A kind of bionic flexible body mechanism for quadruped robot is proposed, which is composed of one bionic spine and four pneumatic artificial muscles(PAMs). This kind of body imitates the four-legged creatures' kinematical structure and physical properties, which has the characteristic of changeable stiffness, lightweight, flexible and better bionics. The kinematics of body bending is derived, and the coordinated movement between the flexible body and legs is analyzed. The relationship between the body bending angle and the PAM length is obtained. The dynamics of the body bending is derived by the floating coordinate method and Lagrangian method, and the driving force of PAM is determined. The experiment of body bending is conducted, and the dynamic bending characteristic of bionic flexible body is evaluated. Experimental results show that the bending angle of the bionic flexible body can reach 18°. An innovation body mechanism for quadruped robot is proposed, which has the characteristic of flexibility and achieve bending by changing gas pressure of PAMs. The coordinated movement of the body and legs can achieve spinning gait in order to improve the mobility of quadruped robot.

  15. Body stability and muscle and motor cortex activity during walking with wide stance

    PubMed Central

    Farrell, Brad J.; Bulgakova, Margarita A.; Beloozerova, Irina N.; Sirota, Mikhail G.

    2014-01-01

    Biomechanical and neural mechanisms of balance control during walking are still poorly understood. In this study, we examined the body dynamic stability, activity of limb muscles, and activity of motor cortex neurons [primarily pyramidal tract neurons (PTNs)] in the cat during unconstrained walking and walking with a wide base of support (wide-stance walking). By recording three-dimensional full-body kinematics we found for the first time that during unconstrained walking the cat is dynamically unstable in the forward direction during stride phases when only two diagonal limbs support the body. In contrast to standing, an increased lateral between-paw distance during walking dramatically decreased the cat's body dynamic stability in double-support phases and prompted the cat to spend more time in three-legged support phases. Muscles contributing to abduction-adduction actions had higher activity during stance, while flexor muscles had higher activity during swing of wide-stance walking. The overwhelming majority of neurons in layer V of the motor cortex, 82% and 83% in the forelimb and hindlimb representation areas, respectively, were active differently during wide-stance walking compared with unconstrained condition, most often by having a different depth of stride-related frequency modulation along with a different mean discharge rate and/or preferred activity phase. Upon transition from unconstrained to wide-stance walking, proximal limb-related neuronal groups subtly but statistically significantly shifted their activity toward the swing phase, the stride phase where most of body instability occurs during this task. The data suggest that the motor cortex participates in maintenance of body dynamic stability during locomotion. PMID:24790167

  16. Body stability and muscle and motor cortex activity during walking with wide stance.

    PubMed

    Farrell, Brad J; Bulgakova, Margarita A; Beloozerova, Irina N; Sirota, Mikhail G; Prilutsky, Boris I

    2014-08-01

    Biomechanical and neural mechanisms of balance control during walking are still poorly understood. In this study, we examined the body dynamic stability, activity of limb muscles, and activity of motor cortex neurons [primarily pyramidal tract neurons (PTNs)] in the cat during unconstrained walking and walking with a wide base of support (wide-stance walking). By recording three-dimensional full-body kinematics we found for the first time that during unconstrained walking the cat is dynamically unstable in the forward direction during stride phases when only two diagonal limbs support the body. In contrast to standing, an increased lateral between-paw distance during walking dramatically decreased the cat's body dynamic stability in double-support phases and prompted the cat to spend more time in three-legged support phases. Muscles contributing to abduction-adduction actions had higher activity during stance, while flexor muscles had higher activity during swing of wide-stance walking. The overwhelming majority of neurons in layer V of the motor cortex, 82% and 83% in the forelimb and hindlimb representation areas, respectively, were active differently during wide-stance walking compared with unconstrained condition, most often by having a different depth of stride-related frequency modulation along with a different mean discharge rate and/or preferred activity phase. Upon transition from unconstrained to wide-stance walking, proximal limb-related neuronal groups subtly but statistically significantly shifted their activity toward the swing phase, the stride phase where most of body instability occurs during this task. The data suggest that the motor cortex participates in maintenance of body dynamic stability during locomotion.

  17. Scale effects and morphological diversification in hindlimb segment mass proportions in neognath birds

    PubMed Central

    2014-01-01

    Introduction In spite of considerable work on the linear proportions of limbs in amniotes, it remains unknown whether differences in scale effects between proximal and distal limb segments has the potential to influence locomotor costs in amniote lineages and how changes in the mass proportions of limbs have factored into amniote diversification. To broaden our understanding of how the mass proportions of limbs vary within amniote lineages, I collected data on hindlimb segment masses – thigh, shank, pes, tarsometatarsal segment, and digits – from 38 species of neognath birds, one of the most speciose amniote clades. I scaled each of these traits against measures of body size (body mass) and hindlimb size (hindlimb length) to test for departures from isometry. Additionally, I applied two parameters of trait evolution (Pagel’s λ and δ) to understand patterns of diversification in hindlimb segment mass in neognaths. Results All segment masses are positively allometric with body mass. Segment masses are isometric with hindlimb length. When examining scale effects in the neognath subclade Land Birds, segment masses were again positively allometric with body mass; however, shank, pedal, and tarsometatarsal segment masses were also positively allometric with hindlimb length. Methods of branch length scaling to detect phylogenetic signal (i.e., Pagel’s λ) and increasing or decreasing rates of trait change over time (i.e., Pagel’s δ) suffer from wide confidence intervals, likely due to small sample size and deep divergence times. Conclusions The scaling of segment masses appears to be more strongly related to the scaling of limb bone mass as opposed to length, and the scaling of hindlimb mass distribution is more a function of scale effects in limb posture than proximo-distal differences in the scaling of limb segment mass. Though negative allometry of segment masses appears to be precluded by the need for mechanically sound limbs, the positive allometry of

  18. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  19. Strength Training for the Intrinsic Flexor Muscles of the Foot: Effects on Muscle Strength, the Foot Arch, and Dynamic Parameters Before and After the Training

    PubMed Central

    Hashimoto, Takayuki; Sakuraba, Keishoku

    2014-01-01

    [Purpose] The purpose of the present study was to verify the effects of intrinsic foot flexor strength training. [Subjects] The subjects were 12 healthy males without motor system disease. [Methods] A training method that involved flexion of all toe interphalangeal and metatarsophalangeal joints against a 3-kg load was implemented and was performed for 200 repetitions once per day, three times per week, for a period of eight weeks. [Results] Significant changes were observed for intrinsic foot flexor strength scores, foot arches, vertical jumping, 1-legged long jumping, and 50-m dash time. [Conclusion] This muscle strength training method significantly improved muscle strength scores, foot arch shape, and movement performance. PMID:24707086

  20. Strength training for the intrinsic flexor muscles of the foot: effects on muscle strength, the foot arch, and dynamic parameters before and after the training.

    PubMed

    Hashimoto, Takayuki; Sakuraba, Keishoku

    2014-03-01

    [Purpose] The purpose of the present study was to verify the effects of intrinsic foot flexor strength training. [Subjects] The subjects were 12 healthy males without motor system disease. [Methods] A training method that involved flexion of all toe interphalangeal and metatarsophalangeal joints against a 3-kg load was implemented and was performed for 200 repetitions once per day, three times per week, for a period of eight weeks. [Results] Significant changes were observed for intrinsic foot flexor strength scores, foot arches, vertical jumping, 1-legged long jumping, and 50-m dash time. [Conclusion] This muscle strength training method significantly improved muscle strength scores, foot arch shape, and movement performance.

  1. Intracellular Phosphate Dynamics in Muscle Measured by Magnetic Resonance Spectroscopy during Hemodialysis.

    PubMed

    Lemoine, Sandrine; Fournier, Thomas; Kocevar, Gabriel; Belloi, Amélie; Normand, Gabrielle; Ibarrola, Danielle; Sappey-Marinier, Dominique; Juillard, Laurent

    2016-07-01

    Of the 600-700 mg inorganic phosphate (Pi) removed during a 4-hour hemodialysis session, a maximum of 10% may be extracted from the extracellular space. The origin of the other 90% of removed phosphate is unknown. This study tested the hypothesis that the main source of phosphate removed during hemodialysis is the intracellular compartment. Six binephrectomized pigs each underwent one 3-hour hemodialysis session, during which the extracorporeal circulation blood flow was maintained between 100 and 150 ml/min. To determine in vivo phosphate metabolism, we performed phosphorous ((31)P) magnetic resonance spectroscopy using a 1.5-Tesla system and a surface coil placed over the gluteal muscle region. (31)P magnetic resonance spectra (repetition time =10 s; echo time =0.35 ms) were acquired every 160 seconds